The foreign minister of ex-Soviet Belarus, who this year dismissed concerns that Russia would send troops to Ukraine from his country, has died at the age of 64, the Belta news agency reported Saturday.

The Belarusian leadership is a close ally of the Kremlin and allowed Belarusian territory to be used by Moscow's troops to launch a military operation against Ukraine in February.

"The Belarusian foreign minister Vladimir Makei has died suddenly," Belta state news agency reported citing the foreign ministry spokesman Anatoly Glaz.

Makei was 64 years old. He had held his post since 2012.

Earlier this week Makei took part in a summit of the Moscow-led Collective Security Treaty Organisation (CSTO) in Armenia's capital Yerevan.

He was due to meet Russian counterpart Sergei Lavrov in Minsk on Monday.

Belarus, ruled with an iron fist by President Alexander Lukashenko since 1994, borders both Ukraine and Russia.

Makei in February said that "not a single" Russian soldier would remain in Belarus after joint manoeuvres with Russia near Ukraine's border that spurred concerns of a possible attack.

Moscow moved troops into Ukraine a week later, including via Belarusian territory.