A monitoring group says Islamic militants have taken control of most of a large Palestinian refugee camp on the outskirts of Syria's capital, Damascus.
The Yarmouk refugee camp lies just south of Syria's capital, Damascus.
The Syrian Observatory for Human Rights said Saturday that fighters from the Islamic State and al-Nusra Front, al-Qaida's branch in Syria, gained control of about 90 percent of the Yarmouk refugee camp. The two groups fought together against other rebels, including a militia of Syrians and Palestinians who oppose the Syrian government.
In addition to the ground clashes, United Nations officials said Syrian forces were shelling the camp. Violence during the past week has trapped its residents – about 18,000 civilians, including many children – inside the camp.
U.S. condemns attacks on civilians
The United States on Saturday condemned the attacks on Yarmouk. It said the actions of the Islamic State group and its allies are a "severe risk" to civilians who already have been under siege for two years, deprived of deperately needed food, medical supplies and other essentials.
Yarmouk, home to roughly 500,000 Palestinians until the Syrian conflict broke out in 2011, has seen several rounds of ferocious and deadly fighting between government forces and militants since 2012. Thousands of the camp's former residents have fled to Lebanon and Jordan.
In addition to Yarmouk, the U.S. State Department condemned other attacks that have endangered Syrian civilians. Innocent families "continue to suffer from both the [President Bashar al] Assad regime and violent extremist groups," it said in a statement.
The State Department estimated that recent fighting between regime forces and an alliance of Islamist militants killed more than 100 civilians and displaced an estimated 30,000 others.
IS overshadows Syrian capital
The IS group's offensive in Yarmouk gives it a major presence in the capital, bringing it within a few kilometers of Assad's seat of power.
"The situation in Yarmouk is an affront to the humanity of all of us, a source of universal shame," said Chris Gunness, spokesman for the U.N. Relief and Works Agency (UNRWA).
Reuters news agency quoted him as calling the camp's seizure "a test, a challenge for the international community. We must not fail. The credibility of the international system itself is at stake."
The IS group, which rules swaths of eastern Syria and Iraq, is the target of a U.S.-led campaign of airstrikes.