ANKARA, Turkey -- An anti-aircraft shell from Syria hit an empty room of a health center inside Turkey, a private news agency reported Tuesday. No injuries were reported.

The shell pierced through a window of the health center some 200 meters (yards) inside the Turkish border, in the town of Reyhanli and ricocheted five times before hitting a wall, the Dogan news agency reported. An investigation was launched into the incident, the agency said.

Forces of Syrian President Bashar Assad have been battling rebels near the town of Haram, in Syria's Idlib province, across the border from Reyhanli.

Ever since a shell fired from Syria on Oct. 3 slammed into a Turkish border town, killing 5 civilians, Turkey has been firing into Syria in response to similar attacks.

More than 33,000 people have been killed in Syria since the uprising started in March last year.

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  • Political Assassinations

    Political assassinations in Lebanon have occurred with impunity for decades. While Syria has been blamed for many of the killings, no one has been held accountable. In 2005, Syria was widely accused of involvement in the killing of former Prime Minister Rafik Hariri, a wealthy businessman and an influential Sunni politician. Hariri was hailed in Lebanon for rebuilding Beirut after the 15-year civil war. Following his death in a car bomb explosion, Damascus was forced to withdraw its troops and Syria's grip in Lebanon began to slip. <em>Caption: Lebanese Prime Minister Rafik Hariri addresses a news conference at his Paris residence Monday April 15, 1996. (AP PHOTO/Lionel Cironneau)</em>

  • Political Assassinations

    Many Lebanese residents accused Assad's regime of being behind Friday's assassination of Brig. Gen. Wissam al-Hassan, a Sunni, who headed the intelligence division of Lebanon's domestic security forces that has been probing the assassination plot against Hariri. Al-Hassan and his agents have been credited with identifying Samaha, the former information minister, as Syria's link to Lebanon. <em>Caption: Lebanese advertising workers erect a poster of Brig. Gen. Wissam al-Hassan with Arabic writing that reads, "the martyr of Lebanon's dignity," a day after a car bomb attack killed al-Hassan and at least seven others in downtown Beirut, Lebanon, Saturday, Oct. 20, 2012. (AP Photo/Hussein Malla)</em>

  • Hezbollah

    The Iran-backed Hezbollah has been Syria's most powerful ally in Lebanon, particularly since Damascus ended its military presence in Lebanon seven years ago. The Shiite militant group has dominated Lebanese politics for more than a decade and is now in control of the government. In 2006, Hezbollah gained support from Sunnis and Christians during a 34-day war with Israel, although Lebanon's southern villages and towns and the predominantly Shiite suburbs of Beirut sustained heavy damage. <em>Caption: In this Monday Sept. 17, 2012, photo, Hezbollah leader Sheik Hassan Nasrallah speaks to his supporters in a southern suburb of Beirut, Lebanon. (AP Photo/Hussein Malla)</em>

  • Hezbollah

    Opponents of Assad's regime say Syria's embattled president has maintained his influence in Lebanon through allies such as Hezbollah. <em>Caption: In this Monday, Sept. 17, 2012 photo, Hezbollah leader Sheik Hassan Nasrallah, center, waves to his supporters, in the southern suburb of Beirut, Lebanon. (AP Photo/Hussein Malla)</em>

  • Hezbollah

    Since the beginning of the Syrian uprising, Hezbollah has sought to distance itself from the turmoil in Syria, although there have been allegations that the group has sent fighters to help Assad's regime fight rebels. Hezbollah's leader, Sheik Sheik Hassan Nasrallah, has not publicly sanctioned any operations in support of Assad, and warned the mayhem in the neighboring country was out of the group's control. <em>Caption: Lebanese Shiite movement Hezbollah and Amal supporters march with their party flags during a demonstration in the town of Hermel, in the northern Lebanese Bekaa valley, on September 23, 2012. (AFP/GettyImages)</em>

  • Troops On The Ground

    Lebanon's 15-year civil war ended in 1990 with Syrian forces defeating opponents, controlling large parts of the country and installing allied governments in Beirut. Syrian forces moved into Lebanon in 1976 as peacekeepers after the country got engulfed in civil war between Christian and Muslim militias. <em>Caption: Syrian soldiers take position 17 April 1990 in one of West Beirut districts as they have been deployed after heavy inter-Shi'ite clashes between pro-Syrian Amal movement and pro-Iranian Hezbollah militia. (RABIH MOGHRABI & RAMZI HAIDAR/AFP/Getty Images)</em>

  • Troops On The Ground

    Syrians were drawn into the conflict, and clashed with the Israeli troops after the 1982 invasion aimed at driving out Palestinian guerrillas. <em>Caption: Israeli children look at the nearby Syrian village of Jebata al-Khashabn as they sit on an old tank near the village of Buqaata at the Israeli side of the border on July 24, 2012 in the Golan Heights. (Photo by Uriel Sinai/Getty Images)</em>

  • Troops On The Ground

    In 2000, Bashar Assad became president of Syria, succeeding his late father, Hafez Assad. Israel withdrew from South Lebanon, increasing pressure on Syria to leave. Syrian troops pulled out five years later, after sweeping street protests following Hariri's assassination. Many in Lebanon and its Western-backers blamed Syria for the killing. Damascus has denied involvement. <em>Caption: In this picture taken on June 13, 2000, Syrian President Bashar al-Assad, right, his brother Maher, centre, and brother-in-law Major General Assef Shawkat, left, stand during the funeral of late president Hafez al-Assad in Damascus, Syria. (AP Photo, File)</em>