Russian Federation announced on Wednesday that Turkish-backed rebels attacked its military bases in Syria.
Ten descended on the air base, three on the naval base.
Last month, Russian President Vladimir Putin made a surprise visit to Syria and declared victory in the long fight against the Islamic State militant group.
The drones that attacked Hmeymim air base earlier this month flew out of the area in the southwest of the de-escalation zone Idlib controlled by the so-called "moderate" opposition, the Krasnaya Zvezda newspaper, the official publication of the Russian Defense Ministry, said on Wednesday.
Turkey on Wednesday warned Iran and Russian Federation to make their Syrian regime ally stop bombing the rebel-held northern Idlib province, as tensions mounted ahead of mooted peace talks later this month. But the Russians have hinted that the technology used was too advanced for local militants, seen as a suggestion it could have been supplied by U.S. forces in the vicinity - something the Pentagon says is "absolutely false".
9 that "any suggestion that US or coalition forces played a role in an attack on a Russian base is without any basis in fact and is utterly irresponsible". It said seven of the drones were shot down by air defense systems and the remaining six were forced to land.
Russian Federation claims the drones used in the attacks had a range of about 30 to 60 miles and on Wednesday said they were launched from the village of Muwazarra, about 50 miles away from Hmeimim.
A monitoring group, the British-based Syrian Observatory for Human Rights, said the attacks were carried out by an Islamist rebel faction that operates in Latakia Province, where the Hmeimim base is located, according to the Associated Press news agency.
It was the first time when terrorists applied a massed drone aircraft attack launched at a range of more than 50 km using modern GPS guidance system.
Pilotless drones carrying explosives attacked Russian bases in Syria over the weekend without causing any casualties or damage, Russia's defence ministry said Monday. In recent months, however, the Russian military brass has become increasingly critical of the US role in Syria, accusing it of protecting militants who can carry out future battles against Assad - a claim the USA has angrily denied.