Russia air strikes 'probably' not in IS areas: US defense chief

US Secretary of Defense Ashton Carter speaks about Russian airstrikes in Syria during a press briefing at the Pentagon in Washington, DC, September 30, 2015 (AFP Photo/Saul Loeb)

Washington (AFP) - Russia's air strikes in Syria on Wednesday "probably" did not target Islamic State jihadists, US Defense Secretary Ashton Carter said, contradicting Russian claims.

"It does appear (the strikes) were in areas where there were probably not ISIL forces," Carter said, using an alternative acronym for the IS group. The Russian defense ministry had said its strikes targeted IS militants.

Russia's military involvement in Syria only risks inflaming the years-old conflict, Carter said.

Moscow's "approach is tantamount... to pouring gasoline on the fire," he said at the Pentagon, hours after Russia launched air strikes in Syria.