A fierce two-day battle in the eastern suburbs of the Syrian capital Damascus has killed more than 160 rebel and regime forces, activists said on Sunday.
The latest fighting in the Eastern Ghouta region came against the backdrop of regime advances in the region that have cut rebel supply lines to the capital and its southern districts. Rebels have been struggling to break the blockade by forces loyal to President Bashar al-Assad.
The Syrian Observatory for Human Rights, a London-based rights group, said the fighting began on Friday when rebel forces launched attacks against checkpoints and military stations in five areas in the region.
"They are trying to break the siege imposed by the army," Rami Abdel Rahman, the director of the group, told AFP news agency.
"It is a ferocious fight between the two sides because it's a struggle over our ultimate fate here," said Bara Abdelrahman, an activist who works with the rebels, according to Reuters news agency.
The battle has also drawn in hundreds of foreign fighters on both sides, activists say.
The Observatory said that the dead included 55 rebel fighters, including seven battalion leaders, and 41 fighters from the al-Qaeda-affiliated Islamic State of Iraq and the Levant and the al-Nusra Front.
At least 36 Syrian regime troops were also reportedly killed, along with 20 members of a Shia Iraqi group fighting alongside the army, and eight members of a Syrian pro-regime militia.
The Observatory said the Lebanese Shia group Hezbollah was fighting alongside regime forces, but gave no details of casualties in its ranks.
In recent weeks, the Syrian army has recaptured a string of areas south of Damascus, turning its attention to both Ghouta and the strategic Qalamoun region north of the capital.
The conflict in Syria has killed more than 100,000 people, according to the United Nations, and is also destabilising Syria's neighbours.