BEIRUT (AP) — A regional official and Syrian activists say Iran and its proxy militia in Lebanon have poured in hundreds of fighters to central and northern Syria in recent days.

They say the Iranian and Hezbollah fighters are taking advantage of Russian air cover to go on the offensive against insurgents in those areas.

Iranian and Syrian officials have long maintained that Iran has advisers and military experts in Syria. Wednesday's news is the first confirmation of Iranian fighters taking part in combat operations in Syria.

The official with knowledge of operational details in Syria spoke on condition of anonymity because he was not authorized to discuss military affairs.

Russia began carrying out airstrikes in Syria on Sept. 30, and Syrian troops and allied militiamen began a ground offensive a week later.