Russia has confirmed that one of its helicopters, with five people on board, has been shot down over the Syrian province of Idlib.
Russia's Interfax news agency said the crew had been returning to its base after delivering aid to the besieged city of Aleppo when it was brought down.
The attack took place around 40km from Aleppo, where rebel groups are involved in an offensive to break a government siege on rebel-held parts of the city.
According to activists, residents are burning tires to create what they describe as a 'smoke curtain' against aerial attacks.
The five aboard the helicopter died a "heroic death" on a humanitarian mission, Kremlin spokesman Dmitry Peskov told a conference call with reporters.
He said the helicopter had tried to veer away from inhabited areas to avoid civilian deaths.
Mr Peskov also said that Moscow would continue fighting international terrorism "on all fronts" despite threats from the so-called Islamic State.
Yesterday, IS posted a nine-minute video message on YouTube, calling on its members to carry out jihad or holy war in Russia.
