Russia's recent air strikes against ISIS in Syria have been praised as a "holy battle" by the Russian Orthodox Church.

Russia launched its second day of air strikes in Syria today, while western leaders struggled to know how to react to Putin's insistence that President Bashar al-Assad must remain in power.

But the head of the the Orthodox Church's public affairs department has reacted positively to the news.

"The fight with terrorism is a holy battle and today our country is perhaps the most active force in the world fighting it," said Vsevolod Chaplin on Interfax news agency.

"Russia took a responsible decision to use military forces to protect the Syrian people from the woes brought on by the tyranny of terrorists," said an official statement from the Church's Patriarch Kirill.

The Patriarch, who often speaks out on political issues in support of the Kremlin, went on to say that armed intervention was necessary because "the political process has not led to any noticeable improvement in the lives of innocent people, and they need military protection."

Elsewhere there has been less positive reaction to Russia's biggest military intervention in the Middle East since the invasion of Afghanistan is 1979.

US-backed Syrian rebels said they had been hit by Russia's air strikes, giving support to fears from Washington that Russia would use its air strikes to target opponents of Assad's regime, not ISIS.

A pro-Assad TV channel reported that Russian aircraft had attacked Jaysh al-Fateh, a powerful rebel coalition who have fought against both ISIS and Assad.

However Sergei Lavrov, Russia's foreign minister, dismissed reports of targeting non-ISIS positions.

"Our targets are solely the positions of objects and equipment belonging to the armed terrorist group Isil [ISIS]," Russia Today quoted Lavrov as saying.