Moscow has around 100,000 troops stationed close to Ukraine's frontier and Western leaders have scrambled to hold talks with Russia fearing an attack.

The Russian defence ministry said 400 of its troops will Friday participate in a "tactical exercise" in the southern Rostov region bordering Ukraine.

Seventy military vehicles, tanks, grenade launchers and unmanned aerial equipment will be involved in the exercises, it said, adding that the soldiers will stage "combat operations".

In a separate statement, the ministry said its Black Sea Fleet also held drills including training on "searching and destroying ships of a mock enemy".

It said this was part of a "combat training plan of the Black Sea Fleet."

Russia, which controls the Crimea peninsula after annexing it from Ukraine in 2014, has made the Black Sea a strategic priority.

Moscow is also holding live-fire drills across Belarus, a Moscow ally which borders Ukraine and the European Union.

NATO has said Russia's deployment of missiles, heavy armour and machine-gun toting soldiers in Belarus are a "dangerous moment" for Europe some three decades after the Soviet Union's collapse.

The war games in Belarus are set to run until February 20.

Western leaders have been shuttling to Moscow in an effort to keep the lines of communication open, with British Defence Secretary Ben Wallace due in the Russian capital Friday.

French President Emmanuel Macron held talks with Russian President Vladimir Putin in the Kremlin this week.