Food prices have soared and families are drinking untreated river water in the Syrian city of Deir al-Zor, the U.N. children’s agency UNICEF said on Monday, as a siege imposed by Islamic State threatens tens of thousands of civilians.

Islamic State militants launched a fierce assault on Syrian government-held areas of Deir al-Zor earlier this month, capturing an area used to supply the city through air drops as the assault cut the state-controlled area in two.

“The escalation of violence threatens the lives of 93,000 civilians, including over 40,000 children who have been cut off from regular humanitarian aid for over two years,” said Geert Cappelaere, UNICEF regional director, in a statement.

“Indiscriminate shelling has reportedly killed scores of civilians and forced others to remain in their homes. Food prices have sky-rocketed to levels five to ten times higher than in the capital, Damascus. Chronic water shortages are forcing families to fetch untreated water from the Euphrates River, exposing children to the risk of waterborne diseases,” he said.

The assault appears to be part of an IS effort to shore up its presence in Syria as it loses ground in Iraq.

Islamic State controls nearly all of Deir al-Zor province, with the government-held part of the city and nearby air base representing the only state-controlled part of the area.

Islamic State encircled the government-held area of Deir al-Zor city in July 2014. Since April 2016, the World Food Programme has completed more than 177 air drops to the city. But these stopped on Jan. 15 when IS seized control of the drop zone to the west of a government air base near the city.