Washington: The United States believes it has killed about 6,000 jihadists in its air strikes against the Islamic State group, defense officials have said.

Pentagon chief Chuck Hagel, however, warned against resorting to "body counts" to measure progress in the war. The estimate of how many IS fighters had been taken out by US-led air raids was first cited by Washington's ambassador to Iraq, Stuart Jones, in an interview aired yesterday by Al-Arabia television.