All the five people aboard a Russian Mi-8 transport helicopter were killed on Monday when the aircraft was downed by hostile ground fire in Syria, said Kremlin spokesman Dmitry Peskov.

"Those onboard the helicopter, according to the Defense Ministry's information, have died heroically as they had tried to steer the machine to minimize the casualties on the ground," Peskov told reporters.

Earlier in the day, the Russian Defense Ministry said the helicopter was shot down in Syria's northwestern province of Idlib by gunfire from the ground while returning to the Hmeimim Air Base after delivering humanitarian aid to the Syrian city of Aleppo.

Among those on board were three crew members and two officers of the Russian center for reconciliation of the opposing sides in Syria, the ministry said in a statement.

The Kremlin said that Russia would continue to combat terrorism in Syria as the Islamic State militant group called on its supporters to wage attacks in Russia in a video clip that was posted online. The video, however, could not be independently verified at the moment.

"Such threats are not able in any way to impact Russia's and President Vladimir Putin's consistent policy on the fight against international terrorism, which of course will continue in all directions," Peskov was quoted by RIA Novosti news agency.

He stressed that terrorist publications were treated with necessary attention by special services responsible for anti-terrorist operation and security.

"The Ministry of Defense overseeing the Aerospace Forces' operations in Syria are taking the necessary measures," Peskov added.

The spokesman also warned against exaggeration of the "scare tactics" used by the terrorists, and noted that "precautions must be taken at the same time."

Russia began to deploy its air forces in Syria at the request of Syrian President Bashar al-Assad in September last year to strike terrorist targets.

In March, Putin ordered the withdrawal of most of its air forces from Syria, but Moscow kept striking terrorist targets and maintained military coordination with the U.S.-led coalition forces, as well as humanitarian aid delivery in the war-torn country.