Rebels have shot down a Russian helicopter in northern Syria, Russian military officials say.

According to defence officials in the country, the Mi-8 transport aircraft had five people on board. Unconfirmed reports say at least four of them are now dead.

The helicopter was returning from delivering humanitarian aid to the city of Aleppo, Russia’s Interfax news agency quoted officials as saying.

However, it is unclear which group brought the helicopter down.

Pictures on social media show wreckage from the crash and charred bodies, with armed men milling around.

Russia is a key backer of Syrian President Bashar al-Assad and is supporting pro-government forces with air strikes on rebels.

Government forces cut off rebel-held eastern parts of Aleppo last month.

Russia and Syria announced the opening of what they called humanitarian corridors for civilians and rebels wanting to surrender, but few people are reported to have used them, fearing they would be targeted.