Belarus's long-standing foreign minister has died suddenly, the state news agency Belta reported on Saturday, two days before he was meant to meet his Russian counterpart.

"Foreign Minister Vladimir Makei has passed away suddenly," Belta reported without giving further detail. Makei had held his post since 2012.

Makei, 64, attended a conference of the Collective Security Treaty Organization (CSTO) - a military alliance of several post soviet states - in Yerevan earlier this week and was due to meet Russian counterpart Sergei Lavrov on Monday.

Before the presidential elections and mass anti-government protests in Belarus in 2020, Makei had been one of the initiators of efforts to improve Belarus' relations with the West and had criticised Russia.