There is a "high demand on fighters" and to make a difference on the ground "they're going to need thousands of mercenaries", says Jason Blazakis, senior research fellow at the Soufan Centre, a US-based security think tank.
On Friday, the Russian defence minister Sergei Shoigu said that 16,000 fighters from the Middle East had volunteered to fight with the Russian army. The Russian president Vladimir Putin gave orders allowing fighters from the Middle East to be deployed in the war.
It has been reported that up to 400 fighters from the Wagner group have been in Ukraine.
The Wagner group was first identified in 2014, when it was backing pro-Russian separatists in the conflict in eastern Ukraine.
The serving Wagner fighter explained that in the first days of the invasion of Ukraine he was sent to the country's second city, Kharkiv, where he said his unit successfully completed a mission without revealing what it was.
"We were then paid $2,100 (£1,600) for a month's work and returned home to Russia," he told the BBC.
