Kenyan President Uhuru Kenyatta led regional and world leaders in mourning former Tanzanian president Benjamin William Mkapa, who passed on on Friday morning at a hospital in Dar es Salaam.
Mr Kenyatta sent his condolences to President John Magufuli, the people of Tanzania and the family of the late, eulogising Mkapa as an "outstanding East African who worked tirelessly for the integration, peace, and progress of the region."
Mwai Kibaki, Kenya's third president, described Mkapa as one of Africa's most illustrious sons.
"Mkapa is a perfect portrait of public-spiritedness replete with valuable lessons for those who serve or wish to serve in the public space. A revolutionary at heart whose efforts to deregulate Tanzania's economy marked the beginning of a new dawn in his country," Mr Kibaki said in a statement.
"The late Mkapa -- a close ally of Tanzania's founding president Mwalimu Julius Nyerere -- distinguished himself as one of the most reputable peace brokers in the region," Mr Kibaki noted.
"In his retirement, Benjamin Mkapa, at some point or other, mediated peace talks in Kenya, the DRC Congo, Zimbabwe, South Sudan and Burundi. Mkapa most certainly played his role in making Africa a better place. May he rest in eternal peace," he added.
Mkapa was part of the Panel of Eminent African Personalities, led by former UN Secretary-General Kofi Annan, who mediated talks that secured a power-sharing agreement between Mr Kibaki and opposition leader Raila Odinga, ending Kenya's 2007/08 post-election violence.
Mr Odinga has mourned Mkapa as a great friend of the Kenyan people, a pan-Africanist, a true believer in South-South Cooperation, and a global statesman.
"Mkapa believed in Regional Integration and championed the revival of the East Africa Community. In his death, Africa has lost a giant," said the former prime minister.
The US Embassy in Dar es Salaam in a tweet eulogised Mkapa as having tirelessly worked to ensure peace and social welfare for people from all walks of life. "His contribution will not be forgotten," said the embassy.
UNAids Executive Director Winnie Byanyima described Mkapa as a "tireless champion for peace and an #AIDS free Africa."
Mkapa, who has died at the age of 81, served as Tanzania's third president from 1995 to 2005.
His death was announced by President John Magufuli in a brief televised statement. The country will observe seven days of mourning during which all flags will be flown at half-mast.
"I will remember him for his great love for the nation, his faithfulness, hard work and performance in building the economy," said President Magufuli.