Tanzania's Vice President Samia Suluhu Hassan was due to be sworn in as president on Friday, a government official said, an historic move that is set to make her the East African country's first female head of state.

Hassan's ascension to the presidency comes after the death of President John Magufuli, 61, whose death due to heart disease was announced on Wednesday, more than two weeks after he was last seen in public.

Magufuli's absence since Feb. 27 had fuelled speculation about his health and sparked rumours he had contracted COVID-19, although officials had denied he was ill.

In a tweet on Friday morning, confirmed by the presidency, government spokesman Hassan Abbasi said Vice President Hassan, 61, will be sworn in at 10 a.m. local time (0700 GMT) on Friday.

According to Tanzania's constitution, the vice president serves out the remainder of the term of a president who dies in office. Magufuli, who was first elected in 2015, secured a second five-year term in polls in October last year.

Described as a soft-spoken consensus-builder, Hassan is poised to be the country's first female president and the first to be born in Zanzibar, the archipelago that forms part of the union of the Republic of Tanzania.

Her leadership style is seen as a potential contrast from Magufuli, a brash populist who earned the nickname 'Bulldozer' for muscling through policies and who drew criticism for his intolerance of dissent.

On Thursday the opposition had called for quickly swearing in Hassan to avoid a constitutional vacuum.