ANKARA, Turkey -- Turkey's military chief vowed Wednesday to respond with more force to any further shelling from Syria, keeping up the pressure on its southern neighbor a day after NATO said it stood ready to defend Turkey.

Gen. Necdet Ozel was inspecting troops who have been put on alert along the 910-kilometer (566-mile) border with Syria after a week of cross-border artillery and mortar exchanges escalated tensions between the neighbors, sparking fears of a wider regional conflict. Turkey has reinforced the border with artillery guns and also deployed more fighter jets to an air base close to the border region since shelling from Syria killed five Turkish civilians last week.

"We responded and if (the shelling) continues, we will respond with more force," the private Dogan news agency quoted Ozel as saying during a visit to the town of Akcakale. He offered condolences to a man who lost his wife and three daughters to a Syrian shell.

Schools in Akcakale reopened Wednesday despite the tense situation. They had been closed due to security concerns.

On Tuesday, NATO chief Anders Fogh Rasmussen said the alliance was ready to defend Turkey, its strongest show of support to its ally since the firing began.

The solidarity is largely symbolic. NATO member Turkey has sought backing in case it is attacked, but despite publicly supporting Syria's rebels, Ankara isn't seeking direct intervention. And the alliance is thought to be reluctant to get involved militarily at a time when its main priority is the war in Afghanistan.

U.S. Defense Secretary Leon Panetta said Wednesday that Washington has sent military troops to the Jordan-Syria border to help build a headquarters in Jordan and bolster that country's military capabilities in the event that violence escalates along its border with Syria.

The revelation raises the possibility of an escalation in the U.S. military involvement in the conflict, even as Washington pushes back on any suggestion of a direct intervention in Syria.

Syrian activists, meanwhile, said the rebel units of the Free Syrian Army took control of Maaret al-Numan, a strategic city along the main highway in Idlib province that connects the central city of Homs with northern city of Aleppo and the capital Damascus.

Rami Abdul-Rahman of the Britain-based Syrian Observatory for Human Rights said the rebels took control of the city late Tuesday. He said the rebels control the western entry into the city while the military is massing troops along the eastern outskirts for a possible counter offensive.

Fadi Yassin, an activist in Maarat al-Numan, told The Associated Press on Skype that rebels are in control of the town, although fierce fighting continued around the military barracks in the eastern part on Wednesday, three days after the FSA launched a "liberation battle," he added.

"The city has been liberated," Yassin said of Maarat al-Numan in Idlib province. "All liberation battles start with small cities and then moves on to the major cities."  

Holding on to Maaret al-Numan would be a significant achievement for the rebels, enabling them to cut the army's main supply route to two battered cities of Aleppo and Homs, both of which came under bombardment from the regime's helicopters and artillery on Wednesday, according to activists.

Turkey's state-run Anadolu Agency reported fighting between Syrian rebels and forces loyal to Syrian President Bashar Assad's regime around the Syrian town of Azmarin, in Idlib province, across from the Turkish border. It said Syrians were fleeing homes in the Azmarin region, some crossing into Turkey on rowing boats over the river Orontes, that runs along the border.

Footage from Anadolu showed three young children scrambling down a river bank on the Syrian side before being taken across to Turkey on a makeshift raft strapped to an inner tube. The children said they were fleeing fighting in Azmarin.

Private NTV television reported that explosions and automatic weapon fire could be heard in Turkey's Hatay province, coming from Azmarin. It said rebels were clashing with some 500 Syrian government soldiers, and that at least 100 rebels had been injured, some of whom had been brought to Turkey for treatment.

Some 99,000 Syrians, mostly women and children, have sought refuge in Turkey since the start of the conflict.

Also on Wednesday, state-run news agency SANA said President Bashar Assad appointed Sattam Jadaan al-Dandah as Syria's new ambassador to Iraq. The report did not say when al-Dandah will travel to Baghdad. His predecessor, Nawaf Fares, defected in July to become the most senior diplomat to abandon Assad's regime during a bloody 18-month uprising that has gradually become a bloody civil war.

Turkish Prime Minister Recep Tayyip Erdogan, who has been fiercely critical of Assad, said Wednesday that Syria was "the bleeding heart of humanity and the whole Islamic world."

Erdogan told a meeting of the Islamic Conference in Istanbul that Turkey had refrained from responding to half a dozen shells from Syria, but when five people were killed last week "we had to retaliate in the strongest way that we could."

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Barbara Surk and Zeina Karam in Beirut and Frank Jordans in Istanbul contributed to this report.

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Captions by the Associated Press.
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  • Syrian Regime

    Despite major defections and a July 18. explosion in Damascus that killed four top generals, including President Bashar Assad's brother-in-law, the regime's inner circle is still powerful and united against the opposition. Assad's inner circle includes his younger brother, Maher, who commands the forces in charge of protecting the capital. It also includes the heads of the four intelligence agencies playing a major role in the crackdown. Although regime forces lost parts of the northern city of Aleppo, Syria's largest, government troops still control most cities, while the opposition dominates large parts of the countryside. <em>Caption: This June 13, 2000, file photo shows Syrian President Bashar Assad, right, his brother Maher, center, and brother-in-law Major General Assef Shawkat, left. (AP Photo, File)</em>

  • Free Syrian Army

    The main rebel fighting force for more than a year, the Free Syrian Army includes lightly-armed volunteer militiamen and defectors from Assad's military. Its overall strength and structure is unclear, but tens of thousands are believed be loyal to the group. The rebels have control over some northern areas, allowing movement of fighters and supplies from Turkey and Lebanon. Anti-Assad forces have failed to maintain any strategic footholds in big cities, being driven back from key neighborhoods in Homs earlier this year and now apparently losing ground in the largest urban center, Aleppo. The battles also suggest only weak direction from central commanders - including Turkey-based Free Syrian Army leader Riad al-Asaad. <em>Caption: In this citizen journalism image provided by Shaam News Network SNN, taken on Sunday, Aug. 12, 2012, Free Syrian Army soldiers pose for a photograph, in Sarmada, Idlib province, northern Syria. (AP Photo/Shaam News Network, SNN)</em>

  • Syrian National Council

    Based in Istanbul, the SNC has emerged as the main political opposition to Assad and has pushed for international recognition as the legitimate representative of the uprising, despite rifts with other Syrian factions. The group also has been hit by internal feuds that have led some senior members to quit. The current leader, Abdelbaset Sieda, is a Swedish-based activist for Syria's minority Kurdish community. The SNC has gained support from many countries in the West and Arab world, but it has not galvanized international backing, and critics complain its senior leadership is made up mostly of exiles out of touch with their homeland. <em>Caption: The members of the Syrian National Council and its head Abdulbaset Sieda, center, arrive for a meeting with Turkey's Foreign Minister Ahmet Davutoglu in Ankara, Turkey, Monday, July 23, 2012.(AP Photo/Burhan Ozbilici)</em>

  • The National Coordination Committee for Democratic Change

    A rival to the SNC, the National Coordination Committee is led by opposition figures inside Syria, many of them former political prisoners. SNC members accuse the group of being far too lenient and willing to engage in dialogue with the regime. In turn, the National Coordination Committee accuses the SNC of being a front for Western powers and willing to open the door to the Muslim Brotherhood and other conservative Islamist factions. <em>Caption: Member of the National Coordination Committee for Democratic Change, Morhaf Mickael speaks during a meeting of Syrian opposition parties in Brussels on Sunday, June 24, 2012. (AP Photo/Virginia Mayo)</em>

  • International Alliances

    On Assad's side are traditional Shiite allies Iran and Lebanon's Hezbollah. <em>Caption: In this photo released by the Syrian official news agency SANA, Iran's Supreme National Security Council, Saeed Jalili, meets with Syrian President Bashar Assad in Damascus, Syria, Tuesday, Aug. 7, 2012. (AP Photo/SANA)</em>

  • International Alliances

    The regime also has important political cover from Russia and China, which have used their Security Council vetoes to prevent U.N. sanctions on Syria. <em>Caption: In this Jan. 25, 2005 file photo, Syrian President Bashar Assad, left, and Russian President Vladimir Putin shake hands during a signing ceremony in the Kremlin, Moscow. (AP Photo/Sergei Chirikov)</em>

  • International Alliances

    The rebels have built an array of regional support that includes the wealthy Gulf states - led by Iran rival Saudi Arabia - and neighboring Turkey, which offers key supply routes. The West also backs the rebel forces, but has so far opposed mobilizing international military support similar to the NATO-led airstrikes that helped topple Moammar Gadhafi's regime in Libya. <em>Caption: From left, Bahrain's Foreign Minister, Sheik Khalid bin AhmedI bin Mohammed al-Khalifa, Saudi Arabia's Foreign Minister Prince Saud al-Faisal, his Turkish counterpart Ahmet Davutoglu and United Arab Emirates' Sheikh Abdullah bin Zayed al-Nahayan seenduring a group photo during the Gulf Cooperation Council (GCC) Foreign ministers meeting in Istanbul, Turkey, Saturday, Jan. 28, 2012 (AP Photo)</em>

  • Foreign Fighters

    Syria has drawn foreign fighters just as other recent conflicts such as Iraq and Afghanistan. No credible count on them exists, but anecdotal evidence suggests foreigners are coming to fight Assad. Rebel commanders downplay the presence of foreign fighters, saying their cause is a purely Syrian uprising. Mohammed Idilbi, a Syrian activist based in Turkey, says foreign ranks include Libyans, Yemenis, Tunisians and Lebanese. On Saturday, Syria's official SANA news agency claimed four Libyans were among rebels killed in Aleppo. <em>Caption: In this Sept. 18, 2011 file photo, former rebel fighters celebrate as smoke rises from Bani Walid, Libya, at the northern gate of the town. (AP Photo/Alexandre Meneghini, File)</em>

  • Extremists

    U.S. officials and others worry that Syria could become a new foothold for insurgents inspired by al-Qaida. Assessing the degree of radical Islamic ideology in the civil war is impossible, but at least one group, the al-Nusra Front, has emerged and declared allegiance to the Free Syrian Army. Al-Nusra, or Victory, has claimed responsibility for several high profile attacks, including a double suicide bombing in March that killed 27 people in Damascus and the execution-style killing of a Syrian television presenter who was abducted in July. On Friday, U.S. intelligence officials said al-Qaida has advanced beyond isolated pockets in Syria and now is building a network of well-organized cells that could include several hundred militants. <em>Caption: This photo shows Al-Qaida's new leader Ayman al-Zawahiri in a still image from a web posting by al-Qaida's media arm, as-Sahab, Wednesday July 27, 2011. Al-Qaida's new leader has lauded protesters in Syria for seeking to topple the regime of President Bashar Assad. (AP Photo/IntelCenter) </em>