"We have informed the Syrian authorities of our decision to halt our operations with GPC (General Petroleum Corporation) in order to comply with sanctions," the company said in a statement.
Syria had initially refused to sign an Arab proposal to send in observers to monitor its forces accused of rights violations by the UN, which says that more than 4,000 people have been killed since March in a protest crackdown.
But in a letter sent to the Cairo-based Arab League late on Sunday as a League deadline was set to expire, President Bashar al-Assad's regime said it will accept monitors if its conditions are met.
"The Syrian government responded positively to the signing of the protocol" on sending observers "based on the Syrian understanding of this cooperation," Syrian foreign ministry spokesman Jihad Makdisi told reporters.
While confirming the receipt of a Syrian government letter outlining the about-face, Arab League Secretary General Nabil al-Arabi said it contained "new demands."
"We've contacted Arab foreign ministers and they have been apprised of the Syrian letter," Arabi said, adding that consultations were under way.
Damascus has refused to sign, arguing the text undermines its sovereignty, prompting the Arab League to slap Syria with sweeping sanctions on November 27 including a halt on transactions with Damascus and its central bank.
The sanctions announced on Saturday put 19 officials on a blacklist for travel to Arab states and froze their assets in those countries, while calling for an arms embargo and halving Arab flights into and out of Syria.
Syria has already been hit by a raft of EU and US sanctions, and last Friday the UN Human Rights Council passed a resolution "strongly condemning the continued widespread, systematic and gross violations of human rights and fundamental freedoms by the Syrian authorities."
Damascus -- which accuses "armed terrorist groups" of fuelling the unrest -- rejected the resolution as "unjust" and said it was "prepared in advance by parties hostile to Syria."
Despite Damascus's offer to accept observers, a rights group accused forces loyal to Assad of committing even more atrocities, saying witnesses reported seeing the bodies of 34 civilians in a square in the central city of Homs.
The Britain-based Syrian Observatory for Human Rights said one activist reported seeing "the bodies of 34 civilians, in a square in the pro-regime neighbourhood of Al-Zahra, who had been abducted by the shabiha on Monday."
The civilians, it said, had been seized from several "anti-regime neighbourhoods" in Homs, which has been targeted by a brutal crackdown on almost nine months of anti-regime dissent.
The Observatory also reported the so-called "shabiha" militiamen on Monday abducted a bus driver and his 13 passengers in Homs province.
Forces loyal to Assad have laid siege to Homs for the past two months.
Seven people were reported killed in the city and province on Monday by gunfire from the security forces, the Observatory said, after a bloody weekend that saw 63 people dead, at least half of them in Homs.
Elsewhere on Monday, mutinous soldiers killed four members of the security forces, including an officer, at the southern protest hub of Dael in Daraa province, the watchdog said.
The Observatory also accused security forces of arresting 18 students on Monday, eight of them for insulting the president.
Meanwhile, a US official said Secretary of State Hillary Clinton will meet Syrian dissidents in Switzerland on Tuesday, as Washington sees Damascus increasingly isolated over its crushing of pro-democracy protests.
A State Department official told reporters that Clinton will meet with seven political opponents of Assad when she visits Geneva following a stop in Vilnius, Lithuania.
Clinton met for the first time with members of Syria's disparate opposition in Washington on August 2.
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