DAMASCUS, Syria -- A local al-Qaida commander was killed Thursday in northern Syria in ongoing clashes with Kurdish militiamen, the second to die in a week of infighting between extremist and moderate rebel factions.
U.N. experts resumed their probe into the use of chemical weapons in Syria's civil war, but the rebel-against-rebel violence may further complicate their work on the ground.
The intensifying power struggle between disparate factions fighting to topple President Bashar Assad is threatening to further encumber a rebellion plagued by divisions and outgunned by the regime.
The Islamic State of Iraq and the Levant, an al-Qaida offshoot consisting mostly of foreign fighters, has sought to expand its influence in opposition held territories, employing brutal tactics and trying to impose Islamic law.
That has created a backlash against the group from more moderate factions concerned that extremists are discrediting their rebellion.
Highlighting the militants' growing muscle, activists said members of the ISIL broke the crosses off two churches and burned the contents of another in the northeastern city of Raqqa, hoisting in their place their group's black Islamic banner.
The action triggered a protest by residents of Raqqa, which fell into rebel hands last year and has since been controlled mostly by extremist factions, according to a resident of the city who identified himself only by his first name, Amir, for fear of reprisals.
The Syrian Observatory for Human Rights confirmed the incident.
The ISIL commander was killed in clashes with Kurdish militiamen in Aleppo province, activists said. Fighting between the two sides in predominantly Kurdish regions of the north has gone on for months, killing hundreds of people on both sides.
The man, identified by the Observatory as a UAE national and the emir -- or local commander -- of Aleppo, died Wednesday night.
On Monday, a top al-Qaida commander was killed in an ambush by rival Western-backed rebels from the Free Syrian Army rebel umbrella group.
Still, several groups operating under the FSA are increasingly aligning themselves with more radical groups.
Nearly a dozen of Syria's powerful rebel factions formally broke with the main opposition group in exile and called for Islamic law in the country Wednesday, dealing a severe blow to the Western-backed coalition.
The radicalization may complicate the mission of U.N. experts who were back in Syria this week to investigate three alleged incidents of chemical weapons use earlier this year, including two in the north.
The inspectors were seen leaving their Damascus hotel in a vehicle convoy on Thursday afternoon, but there was no indication where they went.
Russia, meanwhile, offered Thursday to provide troops to guard facilities where Syria's chemical weapons would be destroyed.
Deputy Foreign Minister Sergei Ryabkov said Moscow is ready to ensure security and help guard facilities, once the chemical weapons are stored for destruction in Syria.
He emphasized that Moscow will not accept the Syrian chemical weapons to be dismantled in Russian territory.
"We believe that it should be dismantled on Syrian territory," Russian news agencies quoted Ryabkov as saying. "We undoubtedly won't deal with it. We believe that the process of its destruction could be efficiently organized on the territory of Syria."
He spoke just hours before diplomats at the United Nations said the five permanent members of the divided U.N. Security Council appeared to have reached agreement on a resolution requiring Syria to dismantle its chemical weapons stockpiles.
The U.S. and Russia have been at odds on how to enforce the resolution.
Russia's deputy foreign minister, Gennady Gatilov, stressed Wednesday that while the resolution will include a reference to Chapter 7 of the U.N. Charter, which allows for military and nonmilitary actions to promote peace and security, it would not contain wording authorizing measures automatically in case of noncompliance.
Assad has agreed to a U.S.-Russian deal to relinquish his chemical weapons stockpile following the Aug. 21 incident near Damascus that killed hundreds.
The United States and its allies insist Assad's troops were responsible and the U.S. has threatened punitive strikes. Assad's government denies the allegations and said the rebels were behind it.
In an informal interview with the Lebanese daily Al-Akhbar newspaper, Assad said his stockpile was a "burden" he was glad to be rid of. He said Syria initially manufactured chemical weapons as a deterrent to Israel's nuclear arsenal.
"Today we have much more important and sophisticated deterrent weapons with which we can blind Israel in a moment," he said.
Also Thursday, a mortar shell slammed into the Iraqi consulate building in central Damascus, killing an Iraqi woman and wounding three, Syrian state media reported.
-- Karam reported from Beirut. Associated Press writer Vladimir Isachenkov in Moscow contributed to this report.