BEIRUT, Jan 23 Russian jets pounded Islamic State in the eastern Syrian province of Deir al-Zor on Monday, seeking to thwart a full-blown assault by the militants against the last district in the region still held by the Damascus government. Six TU-22 strategic bombers carried out air strikes against Islamic State targets near the city of Deir al-Zor, Russia's defence ministry said in a statement. The long-range bombers took off from Russian territory, it said, a rare occurrence as Russia usually launches bombing runs from its air base in the Syrian province of Latakia. Islamic State has launched its fiercest assault in a year to capture the government enclave, a pocket of Deir al-Zor city surrounded by IS territory, in a battle that has killed dozens. The assault has raised fears for tens of thousands of people living in the government-held zone, whose main supply route was cut off when IS severed the road to a nearby air base last week. A military commander in the alliance of forces fighting in support of the Syrian government said recently that Islamic State was seeking to turn Deir al-Zor into a base of operations. The commander urged the U.S.-led coalition and "every air force" to attack Islamic State to stop it moving its convoys in the area, an apparent sign of dissatisfaction with the level of support from the Russian air force there. The Syrian Observatory for Human Rights, a Britain-based war monitor, said Russian air strikes had escalated in Deir al-Zor since Saturday, describing them as intense. Warplanes flew from Russia to hit IS positions in Deir al-Zor on Saturday and returned after the strikes, RIA news agency quoted the Russian defence ministry as saying. CIVILIANS UNDER THREAT The Observatory reported heavy clashes on Monday between government forces and IS fighters, especially around the city's cemetery and a road junction known locally as the Panorama Roundabout. The U.S.-led military alliance against Islamic State also said in a statement that coalition jets had conducted 14 air strikes near Deir al-Zour on Sunday. Food prices have soared and families are drinking untreated river water in Deir al-Zor, the U.N. children's agency UNICEF said on Monday, due to the IS-imposed siege. "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. 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, which began earlier this month, 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 army retaining the air base in the city and neighboring districts, which the jihadists encircled in July 2014. The Syrian government and its Russian ally have since made regular aid drops into the beseiged zone.