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

"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.