President Vladimir Putin has approved deploying up to 16,000 volunteers from the Middle East to fight alongside Russian forces in the invasion of Ukraine.

As Russian troops continue their offensive toward the Ukrainian capital Kyiv from the northwest and east for more than two weeks, Putin on Friday gave the go-ahead to enlist battle-hardened forces from conflicts such as in Syria on Friday.

"If you see that there are these people who want of their own accord, not for money, to come to help the people living in Donbass, then we need to give them what they want and help them get to the conflict zone," Putin said at a televised security council meeting from the Kremlin.

Reports began emerging earlier this week that Russia wanted to recruit fighters in Syria, with the clear danger of Iran-backed forces and other militants going to Europe to fight.

"As to the delivery of arms, especially Western-made ones which have fallen into the hands of the Russian army - of course I support the possibility of giving these to the military units of the Lugansk and Donetsk people's republics," Putin added.

During the meeting, Defense Minister Sergei Shoigu proposed that Western-made Javelin and Stinger missiles that were captured by the Russian army in Ukraine should be handed over to Donbass forces.

Responding in a video message, Ukrainian President Volodymyr Zelensky said "thugs from Syria" would be coming to kill people "in a foreign land".