The surrendered militants said that US instructors had been preparing them for terrorist acts and sabotage at oil and gas and transport facilities, according to the information provided by the Russian military's centre for the Syrian reconciliation.

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. On the border of the 55-kilometer security zone, they were attacked by a detachment of the US-backed Jaysh Maghawir al-Thawra ("Revolutionary Commando Army") radical group.

"According to the testimony of the members of the illegal armed groups who surrendered to the government, the Americans provided them with pickup vehicles and weapons. US instructors trained them to carry out sabotage at oil and gas and transport infrastructure, as well as organise terrorist acts in the territory controlled by the Syrian government forces", he said.

The armed conflict between the Syrian government and opposition groups, including terrorists, began in 2011. By 2016, terrorist forces were significantly subdued, while the government and opposition concluded a ceasefire, with Russia, Iran, and Turkey acting as its guarantors.

Militants remain in control of a small pocket of areas in the Idlib province in northwest Syria.