mARAB states have urged Syrian President Bashar al-Assad to take a "courageous step" and give up power in return for safe passage to end the bloodshed in his country.
Arab League foreign ministers also called on the Syrian opposition and the Free Syrian Army to form a transitional government to ensure a smooth change of power, according to Kuwaiti Deputy Prime Minister Sheikh Sabah al-Khaled al-Sabah.
"President Bashar al-Assad can do more than anyone else to put an end to the destruction and the killings by taking a courageous step," Qatari Prime Minister Hamad bin Jassim al-Thani said, according to the official Qatar News Agency.
The call came as rebels battled government forces in the capital, Damascus, and Syria's largest city, Aleppo.
The Syrian government claimed to have retaken control of Damascus after the 4th Armoured Division, commanded by Dr Assad's younger brother Maher, swept through three rebel-held districts and laid siege to a fourth.
The Israeli military claimed last night that Dr Assad remained in the capital, after rumours that he had fled for the coastal city of Latakia.
US intelligence officials said yesterday that Syrian government forces have moved some of the country's stocks of sarin and VX nerve gas and other chemical weapons. They don't know whether the Syrians are trying to secure the weapons or move them into position to use against the opposition if Dr Assad orders that.
In an apparent attempt to deter a counter-offensive, Turkey has sent batteries of ground-to-air missiles to the border with Syria as rebels took control of three crossing points. Turkey is sheltering thousands of Syrians who have fled the conflict at home.
Turkish Prime Minister Recep Tayyip Erdogan warned last month after the downing of a military jet initially blamed on Damascus that it now regarded Syria as a "clear and imminent threat".
Syria has in turn accused Turkey of sheltering rebels and training and supplying militants fighting the regime in a conflict that erupted in March 2011 and has now claimed at least 19,000 lives, according to activists.
Rebels were now in control of the Jerablus, Bab al-Hawa and al-Salama border posts on the frontier with Turkey, a diplomat and Turkey's Anatolia news agency said.
At the al-Salama border post, about 17 rebel fighters armed with Kalashnikov assault rifles burnt portraits of Dr Assad as rebel leader Ammar Dehdeh gave details of the battle, which he said had lasted for three hours early on Sunday.
"This border post has a strategic importance for the regime, because this area is the most suitable one to set up a buffer zone," said Mr Dehdeh.
The al-Salama post lies north of Aleppo, facing the Turkish border post of Oncupinar near Kilis.