A US-armed Syrian rebel group claims it has hit a Russian military helicopter with an anti-tank missile, forcing it to make an emergency landing.

The helicopter was understood to have been among a number of Russian aircraft searching for the two pilots from an Su-24 jet which was downed by the Turkish military.

According to the Syrian Observatory for Human Rights, Free Syrian Army officials said its fighters successfully targeted the Russian search helicopter with anti-tank weaponry.

The insurgent group is among the recipients of US Tow missiles, among other armaments, designed to bolster it against regime forces.

Unlike the pilots of the Russian jet, the helicopter did not come down within rebel-held territory in the mountainous north-eastern Latakia province where it was hit, the Observatory told Reuters.

Instead, it was reportedly able to make an emergency landing in a nearby government-held area.

What happened to the pilots of the Russian jet remains unclear. While the rebels said they had video and photos showing one had been found dead upon landing near the Turkish border, conflicting reports suggested the second pilot was either missing or also dead.