The Russian army on Friday said it had "eliminated" the militants behind a mortar attack on a base in Syria on New Year's Eve that killed two Russian soldiers.

"The command of our troops in Syria carried out a special operation to find and eliminate the group of militants that carried out the mortar attack on the Hmeimim base (Western Syria)," the Russian defence ministry said in a statement.

Special forces tracked the fighters to their base camp near the border of Idlib province, the statement said.

When the fighters, whose affiliation was not announced, were preparing to leave the base they were "destroyed by a Krasnopol guided missile," according to the ministry.

"A drone assembly and storage area was also discovered" the announcement said.

Ten drones equipped with explosives attacked Russia's airbase in Hmeimim in the early hours of January 6, the military previously reported. There were no casualties.

Russian President Vladimir Putin made a surprise visit to Syria last month where he ordered the start of a pullout of Russian troops, saying their task in the war-torn country had been largely completed.

Three battalions of military police and officers of the Russian Center for Reconciliation would remain in Syria, as well as two Russian bases, Defence Minister Sergei Shoigu said on a subsequent trip.