Belarus’s architect of Western outreach dies suddenly, state media reports.

A top Belarusian official who led a failed attempt to thaw diplomatic relations between the nation’s Kremlin-allied government and the West died suddenly over the weekend, Belarusian state media and government agencies said, amid growing speculation over his country’s involvement in the war in neighboring Ukraine.

Vladimir Makei served 10 years as the foreign minister of Belarus, a key geopolitical battleground between Russia and the West. State media reported on Saturday that Mr. Makei had died at the age of 64, without mentioning the cause of his death.

The muted reaction from officials and the state-controlled media contrasted with Mr. Makei’s status as one of the most prominent Belarusian officials in modern times and one of the longest-serving top allies of the country’s authoritarian president, Aleksandr Lukashenko.

The lack of details, while not unusual under Mr. Lukashenko’s secretive regime, has fueled a flurry of speculation among media commentators over the cause of Mr. Makei’s death.

As foreign minister, Mr. Makei led his country’s outreach to the West, which Mr. Lukashenko had tried playing off against Russia in a bid to maintain political power at home.

A reserve colonel in the army who was fluent in English and German, Mr. Makei was one of the few senior Belarusian officials who could move between nationalist hard-liners and European diplomatic circles, making him a valuable member of Mr. Lukashenko’s team, said Pavel Slunkin, a Belarusian political analyst who had worked under Mr. Makei in the foreign ministry.

“Through him, Lukashenko had found a path to the West,” said Mr. Slunkin, referring to Mr. Makei.

Mr. Makei’s diplomatic efforts were reversed by Mr. Lukashenko’s decision to repress the opposition and violently crack down on mass protests following contested elections in 2020. That rendered the foreign minister, in the eyes of many Belarusians,a symbol of gradual political change that never came, said Mr. Slunkin.

Western sanctions in response to Mr. Lukashenko’s crackdown made Belarus increasingly reliant on Russia and a key ally to President Vladimir V. Putin.

Mr. Putin used Belarus as a staging ground for his February invasion of Ukraine. The Russian military has used Belarusian territory to train troops and treat injured fighters, supply its forces in Ukraine and launch strikes on Ukrainian cities, raising fears among many in Belarus that their country is gradually moving toward direct confrontation with a southern neighbor. And Moscow of late has been pressuring Mr. Lukashenko to get more involved in the faltering military campaign next door.

Mr. Makei had been scheduled to meet his Russian counterpart, Sergey V. Lavrov, later this week.

Mr. Lukashenko has not spoken out about Mr. Makei’s death. The state news agency, Belta, on Saturday published a one-line story saying that the president had offered condolences to Mr. Makei’s family.

Mr. Lukashenko has yet to announce a replacement for Mr. Makei. Analysts believe the choice could offer an indication of how far the president is prepared to push his alliance with Russia.