An intense wave of Russian air strikes hit the Syrian province of Hama and nearby areas in the neighbouring province of Idlib on Wednesday, the Syrian Observatoryfor Human Rights monitoring group said.

Russia, a top ally of Syrian President Bashar al-Assad, started carrying out air strikes in Syria last week saying they were targeting hardline Islamic State militants.

But fighters on the ground and Western countries have said the Russian campaign is mainly focusing on other rebel groups and is aimed at shoring up Assad rather than combating Islamic State.

Russia's Wednesday strikes targeted the towns of Kafr Zita, Kafr Nabudah, al-Sayyad and the village of al-Lataminah in Hama province and the towns of Khan Shaykhun and Alhbit in Idlib, the Observatory said.

Most of Idlib province is held by an insurgent alliance that includes al Qaeda's Syria wing Nusra Front and other Islamist factions and that has put pressure on the Syrian military.

There were also heavy surface-to-surface missile bombardments in the area, said the Observatory, which tracks the conflict using sources on the ground.