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 area followed regime advances in the region that have cut rebel supply lines to the capital. The region has been under siege for more than six months. Rebels reportedly advanced in the recent fighting, seizing some small villages and the government-held town of Deir Attiya.

Assad’s forces responded with three air raids, said the Syrian Observatory for Human Rights.

On Friday, rebel units attacked a string of military checkpoints and stations encircling the opposition-held suburbs. Local and international aid workers say Assad’s forces appeared to be trying to starve out residents – indiscriminately affecting civilians as much as rebel fighters.

"They are trying to break the siege imposed by the army," Rami Abdel Rahman, the director of the Observatory, told news agencies. “This battle has been one of incredible human losses. The fighting is spreading all over the eastern suburbs.”

"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 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 soldiers were also reportedly killed, along with 20 members of a Shiite Iraqi group fighting alongside the army, and eight members of a Syrian pro-regime militia.

The Observatory said Lebanon's Hezbollah was fighting alongside regime forces, but gave no details of the casualties suffered by the Iranian proxy organization.

In recent weeks, the Syrian army has recaptured areas south of Damascus, turning its attention to both Ghouta and the strategic Qalamoun region north of the capital.

The Observatory, a pro-opposition group with a network of activists across Syria, said it had documented about 100 deaths on the rebel side on Friday and Saturday in Eastern Ghouta, and more than 60 among forces fighting for Assad.

But it said there were likely to be more deaths that had not been documented.