The head of the Russian Upper Chamber's Commission for the Protection of State Sovereignty, Andrey Klimov, announced on Friday that military personnel from NATO countries were captured during the battles in Ukraine.

The West "continues its war [against Russia] with the hands of Ukrainians, as well as mercenaries," Klimov said, before adding that military personnel from NATO countries were also involved in the ongoing conflict.

He further stated that Russia already has prisoners among the military personnel of NATO countries and that Moscow will reveal related info "when we conduct trials, and the whole world will see what really happened."

Russia killed up to 30 'Polish mercenaries' in Ukraine

Russia said on Friday that it has killed up to 30 Polish mercenaries fighting for Ukrainian forces in the war-torn country's northeastern region of Kharkov.

The Russian Defense Ministry said its strategic rocket forces "eliminated up to 30 Polish mercenaries" in a strike on the village of Izyumskoe, not far from the city of Kharkov.

Early in March, Ukraine's Foreign Minister Dmytro Kuleba told CNN that around 20,000 international volunteers have traveled to fight Russia in Ukraine.

This comes alongside the 16,000 foreign mercenaries whom Zelensky announced will be fighting in Ukraine. 

Earlier, around 450 extremist Arab and foreign nationals arrived in Ukraine from Idlib to fight against Russia's forces, less than only three days after they left Syria, passing through Turkey.

Relatives of extremists that have arrived in Ukraine told Sputnik that senior fighters from terrorist group Hayat Tahrir al-Sham (the rebranded version of Jabhat Al-Nusra, i.e Al-Qaeda) have held a number of meetings with senior leaders in the Turkistan Islamic Party group and Ansar Al-Tawhid and Hurras al-Din groups, and agreed on allowing a number of all their fighters to enter Ukraine through Turkish soil.