Kenyan President William Ruto and his Tanzanian counterpart Samia Suluhu were among the first to extend congratulations to President Paul Kagame, who won re-election in Rwanda on Tuesday.
Mr Ruto said Kenya "celebrate the sovereign choice of the people of Rwanda" and Ms Suluhu extended "heartfelt congratulations" to Kagame in their messages posted on X, formerly Twitter.
The two regional leaders were joined in the salutations by Presidents Umaro Sissoco Embaló of Guinea-Bissau - who called it a "brilliant re-election" - and Filipe Nyusi of Mozambique.
Mr Kagame won his fourth term in office with an improvement to the 98.7 percent landslide victory he posted in 2017, garnering a staggering 99.2 percent this time round.
"On behalf of the people and Government of Kenya, I have the pleasure to convey warmest congratulations upon your re-election to serve a further term as President of the Republic of Rwanda," Mr Ruto said.
"We celebrate with you the sovereign choice of the people of Rwanda and wish you success as you continue steering your country in the path of peace, stability and posterity.
"I look forward to continuing working with you in regional and Pan-African affairs in strengthening the bonds of solidarity and fraternity between the peoples of Kenya and Rwanda."
Mr Kagame has been at the helm of the central African nation since July 1994 when he led his revolutionary RPA forces to stop a genocide.
He is credited with restoring stability and lifting Rwanda's economy from the ashes of the ethnic cleansing in which more than a million Tutsi and some moderate Hutu were slaughtered in a span of just 100 days in 1994.
Tanzania's Suluhu said she was looking forward to continue working with Mr Kagame in fostering the relations between the two countries and in the pursuit of East Africa’s unity and prosperity.
President Nyusi offered his and Mozambicans' best wishes for Mr Kagame as he assumes the "new mandate in the position overwhelmingly entrusted by the People of Rwanda".
Rwanda's Kagame was among the men who played key roles in the NRA liberation war that brought President Museveni to power before he led the RPA in toppling the regime of Juvenal Habyarimana in the country southwest of Uganda.
