Syrian government troops on Saturday closed all roads leading to the capital, Damascus, after opposition rebels attacked checkpoints in various parts of the city, activists said.
"Around 13 army checkpoints were attacked at the entrances of the capital, Damascus. This prompted the government troops to close areas, especially those leading to the eastern, western and southern suburbs of the capital," Haytham Abdullah, a Syrian activist based in Damascus, told dpa.
He added that government troops were mounting a wide-scale crackdown eight kilometers from Damascus.
The Britain-based Syrian Observatory for Human Rights said that four rebels had been killed in clashes near government offices located between the towns of Harasta and Irbin north east of Damascus.
Syrian state television reported that the army had "destroyed a number of vehicles and motorcycles used by terrorists" in Harasta and Daraya, key pro-rebel areas near Damascus.
Rebels are at pains to seize Damascus airport and a main road leading to it in an attempt to cut supply lines to government troops, say activists.
Both sides have been fighting near the facility for more than a week.
Military commanders of several brigades from the rebel Free Syrian Army have agreed to unify their command.
They selected a 30-member supreme military council, led by General Salim Idriss, in preparation for a decisive battle in Damascus, said activists.
News from Syria is hard to independently verify as authorities have barred most foreign media from the country since an uprising against the rule of President Bashar Assad started in March last year.
In Bahrain, British Foreign Secretary William Hague said there was evidence that the Syrian government could use its chemical weapons stocks in quelling the revolt in the country.
"We are extremely concerned about the stockpiles of chemical and biological weapons, and we are also concerned about evidence during the last couple of weeks that the regime could use them," Hague told reporters in the capital Manama Saturday.
He added that the option of military intervention in Syria had not been "ruled out," but Britain continued to seek a peaceful transition in the war-torn country.
U.S. President Barack Obama warned Damascus earlier in the week that there would be dire consequences if the Syrian regime used chemical weapons.
Assad's government has insisted it would never resort to the use of chemical weapons in the 21-month conflict.
Meanwhile, the newly elected National Coalition of Syrian Revolutionary and Opposition Forces was to meet in Cairo on Saturday for talks on electing a prime minister and members of a transitional government in exile.
The head of the coalition, Mouaz Khateeb, is to join Monday a meeting of the European Union foreign ministers in Brussels, in a move aimed at promoting the status of the opposition grouping.
"The Brussels talks will be crucial, especially as the situation (in Syria) has reached its final stages with rebels pushing forward in their fight to control the capital," a Syrian opposition source, speaking on condition of anonymity, told dpa.
The U.S. and other Western powers have been pressuring the coalition, launched in Qatar last month, to show unity and coordinate with forces fighting to oust Assad's regime.
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