Clashes between Syrian rebels and an armed Palestinian group loyal to President Bashar Assad have raged inside a Damascus refugee camp as opposition fighters pushed deeper into the capital, according to activists.

The rebels fighting to topple the Assad regime have made significant tactical advances in the past weeks, capturing air bases and military installations in and around Damascus.

Their offensive in the Palestinian refugee camp of Yarmouk in southern Damascus, which began on Friday, is aimed at driving the pro-government Palestinian gunmen out of the camp, which would be another blow to Mr Assad and his loyalists.

When the revolt against Mr Assad's rule began in March 2011, the half-million-strong Palestinian community in Syria tried to stay on the sidelines of the conflict.

But as the civil war deepened, most Palestinians backed the rebels, though some groups - such as the Popular Front for the Liberation of Palestine-General Command - have been fighting on the government side.

The Britain-based Syrian Observatory for Human Rights said the violence in Yarmouk is forcing an exodus of Palestinian refugees and Syrians who came to the camp in past weeks to escape violence elsewhere in the city. The Observatory relies on reports from activists on the ground.

Camp residents said several mortar rounds landed inside Yarmouk on Tuesday and gunfire has echoed around the area.

They said there were no Syrian government troops in the camp and that most of the fighting was between rebels and gunmen from the PFLP-GC. The group is led by Ahmed Jibril, a long-time ally of Mr Assad.

The Syrian pro-government Al Watan newspaper said that the army could be preparing an operation "to cleanse the Yarmouk camp of gunmen".

Syrian foreign minister Walid al-Moallem claimed the clashes at the camp were triggered by the al Qaida-linked Jabhat al-Nusra group, which was designated a terrorist organisation by the United States last week.

PA