The Islamic State extremist militia Saturday advanced into parts of a Palestinian refugee camp on the outskirts of the Syrian capital Damascus, following two days of fighting against Islamist rivals, a monitoring group reported.
The Syrian Observatory for Human Rights said that Islamic State fighters had seized some parts of the Yarmuk camp, located on the southern edge of Damascus, from al-Nusra Front, the Syrian branch of al-Qaeda.
The Britain-based watchdog reported unspecified casualties among both feuding sides.
Islamic State's incursion into the sprawling camp is seen as an attempt by the al-Qaeda splinter group to make up for the ground it has recently lost elsewhere in Syria.
Last month, Syrian regime forces, backed by Russian warplanes, drove Islamic State from the ancient city of Palmyra, which the militants had controlled for 10 months.
Abu Rami, an activist based in the Yarmuk camp, said that the sound of heavy machine-gun fire could be heard echoing across the grounds.
"Islamic State is trying to make up for the losses they have also suffered in the past two days in northern Syria and near Damascus," Abu Rami told dpa by phone.
He added that the fighting, which is still going on, had forced dozens of residents to flee the camp for safer areas.
"The remaining residents in the camp now feel terrified."
In April 2015, Islamic State briefly seized large parts of Yarmuk before armed Palestinian factions living in the site pushed them back.
Yarmuk lies just eight kilometres south of the centre of Damascus.
Should Islamic State gain control of the camp, it would become the radical movement's closest point to the heart of the regime of Syrian President Bashar al-Assad.
Yarmuk was home to some 150,000 Palestinian refugees before Syria's 2011 uprising. The figure has since dwindled to 18,000 because of the violence, according to the UN.
Since 2012, the camp has been under siege by Syrian government troops, who suspect that it is being used as a shelter for opposition rebels.