A group of 27 militants who surrendered to the Syrian army said they had been trained at the US military base, Rear Adm. Oleg Zhuravlev, the head of the Russian Defence Ministry's centre for the Syrian reconciliation, said during a briefing on Wednesday.

The US also provided them with weapons and vehicles, he added.

"As a result of the clash, the militants who broke through lost three pickups, 27 people escaped, they are currently under the protection of Syrian government forces in Palmyra. They surrendered dozens of small arms, grenade launchers and heavy machine guns, including Western-made ones", Zhuravlev said.

On the night from 13 to 14 April, a group of militants, who were trained at the US forces' base in the vicinity of the Rukban camp, tried to get out of At-Tanf area. The militants planned to surrender to government and return to civilian life, Zhuravlev said.