Vietnam Sunday announced a state funeral and two days of national mourning for President Tran Dai Quang, who died Friday aged 61.
Flags will be flown at half-mast and entertainment venues shut for two days starting September 26, when Quang's body will lie in state in Hanoi before being buried in his home town in Ninh Binh province the next day.
"His passing away is a great loss for our party, state and people," the Communist Party of Vietnam said in a statement Sunday, adding that the funeral would be broadcast live.
Condolences have poured in from across geopolitical divides, with Cuba announcing its own mourning period and US President Donald Trump calling him a "great friend of the United States" in a statement Friday.
The leaders of Cambodia and China also sent tributes, even though Quang's time in office since 2016 was marked by tensions with Beijing over disputed waterways in the South China Sea.
The cause of death was identified in state media as a "rare virus" though no further details were provided.
Vice President Dang Thi Ngoc Thinh will take over as head of state -- the first female in the position -- until a replacement is decided by lawmakers at an unspecified date.
Quang, a former police chief and communist party stalwart, spent more than four decades as an intelligence official and most recently threw his weight behind a crackdown on dissent and corruption which critics say was aimed at rivals.
Though he was a member of the powerful politburo, his role was largely ceremonial, hosting world leaders and diplomatic summits and functions intended to boost Vietnam's profile on the international stage.
Most notably he greeted Trump and Russia's Vladimir Putin at an APEC gathering in Danang in November.
Analysts do not expect his death to shake up politics in the one-party state and rights groups said his legacy was one of repression.
But some in his home town of Quang Thien Commune remembered him fondly.
Reverend Thich Minh Tong, at Dong Duc Pagoda in Ninh Binh's Kim Son district, told AFP Sunday the president had visited and was "very friendly to everyone".
"The country has had many presidents in the past, but President Quang is the only one from our province Ninh Binh. And when he met all the monks, he shook hands with all of them," he recalled.
"When we heard the news of him passing away, everybody feels emotional. We feel sorry and miss him."
Buddhist prayer ceremonies were held over the weekend, including a gathering of hundreds of monks who bowed before a portrait of Quang in a Ho Chi Minh City pagoda on Sunday.