Ethiopian PM, Meles Zenawim
Ethiopian Prime Minister Meles Zenawi has died at the age of 57, state media say, after weeks of illness.
A government spokesman said Meles had died in a hospital abroad - but did not say exactly where or give details of his ailment, reports the BBC.
Speculation about his health mounted when he missed an African Union summit in Addis Ababa last month.
Meles took power as the leader of rebels that ousted communist leader, Mengistu Haile Mariam in 1991.
He had dominated Ethiopian public life since the 1990s, as president and then prime minister.
He was austere and hardworking, with a discipline forged from years spent in the guerrilla movement - and almost never smiled, says Elizabeth Blunt, the BBC's former correspondent in Addis Ababa.
Kenya's Prime Minister Raila Odinga told the BBC he feared for the stability of Ethiopia following Meles' death. He said the situation in the country was fragile and ethnic violence continued to be a threat.
Ethiopia's Council of Ministers announced "with great sadness the untimely death of Prime Minister Meles Zenawi" in a statement, state TV reported.
"The premier [had] been receiving medical treatment abroad for the past two months and his health was improving, but due to a sudden infection which occurred [on Sunday], he went back to hospital for emergency treatment, and even if a lot of medical attention was given by his doctors, he died yesterday at around 23:40," the statement said.
Deputy Prime Minister Hailemariam Desalegn, who is also Ethiopia's foreign minister, will be acting head of government, state television said.
"Even if Ethiopia has been badly affected for missing its great leader, Prime Minister Meles Zenawi initiated fundamental policies and strategies which will be further strengthened," the TV said.
Meles had not been seen in public for some eight weeks prior to his death, and was reported to have been admitted to hospital in July.
But three weeks ago, government spokesman, Bereket Simon told the BBC that he was in "a good condition and recuperating", and dismissed reports he was critically ill.
At the time he declined to give any details about Meles' whereabouts or what he was suffering from.
Some reports suggested Meles was in hospital in Belgium, suffering from a stomach complaint. Other reports said he was in Germany.
Under Meles, Ethiopia became a staunch US ally, receiving hundreds of millions of dollars in aid over the years, and hosting the US military drones that patrol East Africa.