BEIRUT — Heavy government shelling of rebel positions near the Syrian capital killed 16 people on Saturday, activists said, as U.S. Secretary of State John Kerry lobbied European allies to back Washington's proposed military action against the ruling regime.

The Britain-based Syrian Observatory for Human Rights said the mortar and artillery fire on the Moldokhiya agricultural area south of Damascus killed 14 rebels. A child and another civilian also died in the shelling, it added.

The group also reported heavy fighting between rebels and troops loyal to President Bashar Assad around the Christian village of Maaloula northeast of Damascus. The rebel advance into the area this week was reportedly spearheaded by al-Qaida-linked fighters, exacerbating fears among Syrians and religious minorities in particular that Islamic extremists are playing an increasingly important role in the rebellion.

Fighters from the Western-backed Free Syrian Army also have participated in battles around Maaloula, destroying two government checkpoints near the town earlier this week, according to a statement by the main opposition coalition on Friday.

The fighting comes as President Barack Obama's administration pressed ahead with efforts to win congressional backing and international support for military strikes against Syria over an alleged chemical attack in August outside Damascus. The U.S. says Assad's forces fired rockets loaded with the nerve agent sarin on rebel-held areas near the capital before dawn on Aug. 21, killing at least 1,429 people. Other estimates put the death toll from the attack at more than 500.

Obama, back in Washington after a trip to Europe that included a two-day visit to Russia to attend a Group of 20 summit, will intensify his efforts to sell a skeptical Congress and a war-weary American public on a military strike against Syria.

A passionate debate is already underway in Congress and the administration's lobbying campaign culminates Tuesday, the evening before a critical vote on the possible Syria action is expected in the Senate. Obama will address the nation from the White House that night to make his case for military action.

In Lithuania, Kerry met with European leaders, who have been skeptical about whether any military action against Assad's regime can be effective.

In a joint statement Saturday, European foreign ministers agreed with the U.S. that the Aug. 21 alleged chemical attack appears to have been the work of the Syrian regime. But, they added, any potential military attack against Syria should wait for a U.N. inspectors' report.

EU foreign affairs chief Catherine Ashton said that the available intelligence "seems to indicate strong evidence that the Syrian regime is responsible for the attack."

The report from the U.N. inspectors, who collected evidence in the suburbs hit by the Aug. 21 attack, is expected later this month, although some European officials are asking the U.N. to speed up the probe or issue an interim report.

Later Saturday in Paris, Kerry pressed the administration's case further, saying "this is not the time to be silent spectators to slaughter."

France, which firmly backs the Syrian rebels and has strategic and historic interests in the region, had been ready to take military action last week but held off after Obama declared he would seek the backing of Congress first.

The prospect of a U.S.-led strike against Syria has raised concerns of potential retaliation from the Assad regime or its allies. On Friday, the State Department ordered nonessential U.S. diplomats to leave Lebanon over security concerns and urged private American citizens to depart as well.

The Shiite militant group Hezbollah, an Assad ally that has sent fighters into Syria, is based in Lebanon.

On Saturday, dozens of people protested outside the U.S. Embassy against military strikes on Syria. Some of the demonstrators carried placards reading "No War," and "Hands off Syria."

Syrian officials have been trying to capitalize on reluctance in Europe and the U.S., and both the government and state media accuse Obama of "supporting terrorism."

"Any US aggression against Syria has no explanation other than (that it's) supporting terrorism," Syrian Deputy Foreign Minister Faisal Mekdad said in an interview with state-run Al-Ikhbariya TV broadcast late Friday. He challenged the international community to present evidence that Syria had used sarin, and said military action against his country would be "dangerous and might affect America's friends and the entire world."

At the Vatican, an estimated 70,000 people answered Pope Francis' call for a four-hour Syria peace vigil late Saturday, joining Christians as well as non-Christians in similar vigils around the world.

The turnout in St. Peter's Square was believed to be one of the largest rallies in the West against proposed U.S.-led military action.

Francis spent most of the vigil in silent prayer, but during his speech he issued a heartfelt plea for peace : "This evening, I ask the Lord that we Christians, and our brothers and sisters of other religions and every man and woman of good will, cry out forcefully: Violence and war are never the way to peace!"

___

Associated Press writers Deb Riechmann and Raf Casert in Vilnius, Lithuania, Josh Lederman in Washington, Nicole Winfield in Vatican City and Albert Aji in Damascus, Syria, contributed to this report.

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