Palestinian officials and activists say fighters from the Islamic State of Iraq and the Levant (ISIL) group have re-entered and taken control of most of a southern neighbourhood in the Syrian capital, Damascus.

Members of the ISIL stormed the district known as the Yarmouk camp on Wednesday but were expelled on Thursday before re-entering the camp on Friday.

Palestinian official Khaled Abdul-Majid said the group was in control of half of the district.The London-based Syrian Observatory for Human Rights, which monitors the Syrian conflict through a network of activists, also reported new advances by the group in the camp.

Abdul-Majid and another official, Anwar Raja, said ISIL members were fighting a Palestinian faction called Aknaf Bait al-Maqdis. Activists said Bait al-Maqdis had been surrounded by ISIL and confined to a few streets.

Yarmouk, set up as a camp for Palestinian refugees in 1957, has with time developed into a residential neighbourhood inhabited by both Palestinians and Syrians.

Residents said the ISIL advance followed the arrest of group members accused of assassinating a leading figure of Bait al-Maqdis.

Palestinian factions and Syrian armed groups are among groups fighting for the control of the camp. Others include the Nusra Front, Ahrar al-Sham and Free Syrian Army brigades.

US condemnation

The United States condemned attacks against civilians in Syria, including that in Yarmouk.

"The United States strongly condemns attacks this week against Syrian civilians, who continue to suffer from both the Assad regime and violent extremist groups," State Department spokeswoman Marie Harf said.

"We also condemn and are deeply concerned by ISIL's attacks this week against the besieged Yarmouk Palestinian refugee camp in southern Damascus," Harf added in the statement.

Yarmouk was once a thriving area home to 160,000 people but has been caught up in the country's fighting and besieged by regime forces for more than a year.

About 18,000 residents are estimated to in the camp after many fled the fighting.

The siege has caused significant shortages of food, water and medicine inside the camp.

ISIL's rapid advance across Syrian and Iraqi territory has stagnated since an American-led coalition began an air campaign against the group.