Pilotless drones carrying explosives attacked Russian bases in Syria over the weekend without causing any casualties or damage, Russia's defence ministry said Monday.

"Ten drones carrying explosives attacked the Russian air base at Hmeimim and three others targeted the Russian naval base in Tartus", both in western Syria, the ministry said in a statement run by Russian press agencies.

The "terrorist" attacks took place on Friday night causing "neither casualties nor material damage", the statement said.

"The Hmeimim and Tartus bases continue to operate normally," the ministry added.

Of the 13 drones used in the attacks, seven were destroyed while the six others were intercepted by the Russian army, it said.

The statement comes days after Moscow announced that two Russian servicemen were killed in a mortar attack by Islamist militants at the Hmeimim air base on New Year's Eve.

According to the Russian Kommersant business daily, seven military planes were "practically destroyed" in that attack, but the ministry dismissed the report as "fake".

The Syrian Observatory for Human Rights reported that Russian forces were on alert following drone attacks on the Hmeimim base, the largest Russian military base on Syrian territory.

After two years of Russian military support for the regime of Syrian leader Bashar al-Assad, President Vladimir Putin announced in mid-December the partial withdrawal of forces from the country, saying their task in the war-torn country had been largely completed.

The size of the Russian deployment in Syria is not known but independent Russian military expert Pavel Felgenhauer told AFP that up to 10,000 troops and private contractors could have taken part in the conflict.

More than 330,000 people are estimated to have been killed in the Syrian war, which began in 2011 as the regime brutally crushed anti-government protests. Millions have been displaced.

Source:AFP