"Despite doctors' efforts both Russian servicemen died of their wounds," the ministry said in a statement carried by Russian news agencies.

Earlier Friday Belarus and ally Russia held joint military drills near the western border with Poland where a migrant crisis is unfolding.

Belarus's defence ministry said a "joint battalion tactical group" of paratroopers from both countries staged exercises at the Gozhsky range in western Belarus.

The ministry said the drills were carried out due to the "build-up of military activity" near the border.

Russian Il-76 aircraft and Belarusian military helicopters were involved in the drills, where servicemen were carrying out a "number of combat training tasks", it added.

The defence ministry in Moscow said it had sent paratroopers to Belarus for joint exercises as part of a "surprise combat readiness check".

Hundreds of migrants, mainly Kurds, have been stuck for days on the Belarus-Poland border in near-freezing temperatures, with aid groups warning of a looming humanitarian catastrophe.

Western states accuse the Belarusian government of luring them to the country and sending them to cross into Poland in retaliation for previous sanctions over Minsk's crackdown on the opposition.