Heavy fighting has been reported in the heart of Damascus, with the main highway to the south of the country severed, news agencies have reported. On Sunday, the country's international airport was shut down by the clashes.
Some of the worst fighting since the 16-month civil war began in March 2011 were seen about a mile from the airport highway Monday morning. The UK-based Syrian Observatory for Human Rights said the fighting was centered in the Damascus districts of Tadamon, Midan and Kfar Souseh.
"It seems there is a new strategy [by the Free Syrian Army] to bring the fighting into the center of the capital,” opposition activist Mustafa Osso told reporters. "The capital used to be safe. This will threaten the regime.”
There have been reports that opposition forces currently control more than 50 percent of the country.
Some 200,000 Syrian refugees have managed to cross the southern border and fled to safety in Jordan. Thousands more have done the same in the north and east, fleeing to the neighboring countries of Lebanon and Turkey.
Morocco said Monday it had asked Syrian Ambassador Nabih Ismail to leave and declared him persona non grata, calling for a transition to democracy that would meet the Syrian people's aspirations for freedom.
Earlier in the day, rumours had circulated that the ambassador to Rabat, had also defected to the rebel side. A Syrian embassy official denied this but had no further comment.
Morocco's foreign ministry did not immediately explain the timing or the reason for its decision to expel Ismail, but said in a statement the situation in Syria "cannot remain as it is".
It added that Morocco wished for "an efficient and resolute action to ensure a political transition towards a democratic setup that guarantees Syria's unity, stability and regional safety to achieve the brotherly Syrian people's aspirations for dignity, freedom and development."
Morocco recalled its own ambassador to Damascus in November 2011. Monday's decision was the latest in a series of diplomatic expulsions that has seen Damascus increasingly isolated as anti-Assad rebels gain strength.
Reuters news service contributed to this report