Vietnamese President Tran Dai Quang has died at the age of 61 after a serious illness, the government said.

Mr Quang died despite “utmost efforts to treat him by Vietnamese and foreign professors and doctors and care by the party and state leaders”, the statement said.

It said Mr Quang – the country’s number two after the ruling Communist Party leader – died at a military hospital in Hanoi, but did not elaborate on his illness.

The state-run online newspaper VnExpress quoted a former health minister and the head of a national committee in charge of leaders’ health, Nguyen Quoc Trieu, as saying Mr Quang had contracted a rare and toxic virus in July last year and had travelled to Japan six times for treatment.

Mr Trieu said the president lapsed into a deep coma hours after being admitted to the National Military Hospital 108 on Thursday afternoon.

“Japanese professors and doctors treated him and helped consolidate the president’s health for about a year,” Mr Trieu said. “However, there are no medicines in the world that can cure the illness completely, instead it only could prevent and push it back for some time.”

Mr Quang hosted Donald Trump during his first state visit to the communist country last year, when the US president attended a summit of Pacific Rim leaders.

His last public appearance was at a Politburo meeting of the ruling Communist Party and a reception for a Chinese delegation on Wednesday. He looked frail on the state-run Vietnam Television broadcast.

Mr Quang did not appear in public for more than a month last year, raising speculation about his health.

Born in northern Ninh Binh province, he attended a police college and rose through the ranks at the powerful Ministry of Public Security before being appointed as a minister in 2011.

A career security officer and four-star general, Mr Quang was elected president in April 2016 by the Communist Party-dominated National Assembly, effectively becoming the second most powerful man in the country after General Secretary Nguyen Phu Trong.

Phil Roberston, deputy Asia director at Human Rights Watch, said he would be remembered for “a multi-year crackdown on human rights and putting more political prisoners behind bars in Vietnam than any time in recent memory”.

Some 97 activists had been jailed as of April this year, according to Amnesty International.

The National Assembly is scheduled to convene a session next month and is expected to elect a new president.