Syrian forces and tanks gathered outside the Palestinian Yarmouk refugee camp in the capital Damascus today, after at least 25 people were killed in an airstrike on a mosque in the camp on Sunday.

The upsurge in violence prompted a rare intervention by Palestinian President Mahmoud Abbas, who warned the Syrian administration not to drag the 500,000-strong Palestinian population in Syria into the now 21-month old civil war.

On a visit to Rome, where he met the Pope, Mr Abbas said that the Palestinian Authority was, "following, with great concern, the fact that our people are being forced into the unfortunate conflict in Syria." The Palestinian Prime Minister, Salam Fayyad condemned the attack, saying that Assad should "keep them [Palestinian refugees] out" of the fighting.

Many of the Palestinians living in Syria live in the Yarmouk camp in the south of Damascus. Both rebel forces, and those loyal to Assad, have tried to enlist the Palestinians, and in recent weeks there have been clashes between those fighting for each side. Heavy fighting broke out almost two weeks ago between forces loyal to the administration and the Syrian rebels, together with a brigade of Palestinian fighters known as Liwaa al-Asifah, or Storm Brigade.