Russia has accelerated its drive to recruit Syrians to fight for Libya’s rebel leader Khalifa Haftar in May in violation of a UN arms embargo, Reuters reported Sunday.

Haftar’s forces retreated from one of their last strongholds on the outskirts of the Libyan capital of Tripoli last week, ending his 14-month offensive against the country’s UN-backed government. The Tripoli-based Government of National Accord (GNA) declared a fresh offensive to build upon a string of recent successes against Haftar’s men.

Russian private mercenary group Wagner is hiring Syrians to fight for Haftar under the supervision of the Russian military, Reuters cited two unnamed Syrian opposition sources and a regional source as saying.

The Syrian Observatory for Human Rights monitoring group said Russia had recruited more than 900 Syrians to fight in Libya in May, Reuters reported. The recruits are trained at a base in Homs before being deployed to Libya and are paid between $1,000 and $2,000 a month, according to Reuters.

“The pace of hiring increased as Libya’s fighting intensified and the war in Syria died down,” the news agency cited a regional source as saying,