BEIRUT - Syria's Foreign Minister Walid al-Moualem told UN Secretary-General Ban Ki-moon Palestinians should not offer "shelter or assistance to terrorist groups" in the Yarmouk refugee camp in Damascus, state television said on Monday.His comments came after Ban's spokesman said the secretary-general was concerned at reports of an air strike by President Bashar Assad's forces on Yarmouk on Sunday in which activists said 25 people were killed.Syrian jets bombed the camp on Sunday killing at least 25 people.Syrian troops backed by tanks gathered on Monday outside Yarmouk, scene of clashes between Palestinians loyal to Assad and rebels supported by Palestinian fighters, activists said.Moualem said Palestinians should work to expel "terrorists" - the label authorities give to anti-Assad rebels.Syrian troops backed by tanks gathered outside the Palestinian Yarmouk refugee camp in Damascus on Monday, the scene of clashes between Palestinians loyal to President Bashar Assad and rebels supported by Palestinian fighters, activists said.Clashes inside the camp continued on Monday with thousands of people fleeing to nearby suburbs. Hundreds of Palestinians refugees living in Syria flooded into Lebanon on Monday after clashes raged between Palestinian factions loyal to and opposed to President Bashar Assad in a district of Damascus. A Reuters witness at the border said they came in buses and cars piled high with belongings. A Lebanese security source said the refugees from Damascus' Yarmouk Camp suburb had tried to flee on Sunday but the road was blocked by fighting.Yarmouk, in southern Damascus, falls inside a swath of territory that stretches from the east to the southwest of the Syrian capital where Assad's forces have been trying to push back rebels from the gates of his power base for several weeks.Arab League chief Nabil Elaraby on Monday urged all sides in the conflict to protect the Palestinians and to keep them out of the fighting. Syria hosts more than 500,000 Palestinian refugees, most of them in Yarmouk. Assad's government and Syrian rebels have enlisted and armed Palestinians refugees during the 21-month uprising, which has escalated into a civil war.The United Nations Relief and Works Agency for Palestine Refugees (UNRWRA) also said in a statement Monday that it is following the events in the Palestinian camp with "extreme concern," warning that all parties involved in the conflict must "respect their [Palestinian] neutrality, official Palestinian News Agency WAFA reported.Heavy fighting broke out 14 days ago between Palestinians loyal to Assad and Syrian rebels, together with a brigade of Palestinian fighters known as Liwaa al-Asifah (Storm Brigade).The fighting intensified on Saturday with rebels gaining ground inside the camp, forcing Ahmed Jibril, a veteran leader of a Damascus-based Palestinian faction that back Assad to leave the capital with his son. Jibril's PFLP-GC has maintained strong ties to Assad throughout the uprising, unlike the Islamist Hamas movement whose Damascus-based officials - including leader-in-exile Khaled Mashaal - quietly pulled out of Syria as the mainly Sunni Muslim revolt against Assad gained momentum.