Tanzania's former President Benjamin Mkapa, who served from 1995 to 2005, died in the early hours of Friday, President John Pombe Magufuli said in a statement.

Mkapa, Tanzania's third president who led several regional peace mediation efforts in office and afterwards, died while receiving treatment at a hospital in Dar es Salaam, Magufuli said, without giving more details.

"I will remember him for his great love for the nation, his piety, hard work and performance in building the economy," Magfuli said.

The president declared a seven-day mourning period, during which all flags will be flown at half-mast.

"Magufuli asks all Tanzanians to remain calm, patient and united during this difficult time," a statement from his office said.

Mkapa, 81, also served as an ambassador, minister and key official of the ruling CCM party, Magufuli said.