Ethiopian Prime Minister Meles Zenawi, who led the Horn of Africa country for more than two decades, died of an infection while being treated abroad for an undisclosed illness, state-run television said on Tuesday.
Speculation that Meles, 57, was seriously ill grew after he failed to attend an African Union summit in the Ethiopian capital Addis Ababa last month.
"Prime Minister Zenawi suddenly passed away last night. Meles was recovering in a hospital overseas for the past two months but died of a sudden infection at 11:40 (on Monday night)," state television said.
Meles seized power in 1991 from Mengistu Haile Mariam's military junta. As president and then prime minister he turned Ethiopia into a key player in regional security affairs.
His forces, widely regarded as among the strongest on the continent, have entered Somalia twice to battle Islamist militants, winning him accolades from the West for supporting its fight against al-Qaeda linked groups.
State media said Deputy Prime Minister Hailemariam Desalegn would be the acting prime minister. Television broadcast footage of Meles against a backdrop of solemn, instrumental music.
Ethiopia's government said last month that Meles was taking a break to recover from an unspecified condition. Diplomats in Addis Ababa had said Meles was being treated in Brussels for an undisclosed illness, while others said he was in Germany.
During his time in office Meles was credited with steering Ethiopia towards economic growth and also helped mediate in several regional disputes, including rifts between Sudan and South Sudan.
"I believe that any successor to Meles will focus first on domestic issues and for the most part leave the regional and international engagement to other countries, at least until the new leader is firmly established in office," David Shinn, former U.S. ambassador to Ethiopia, told Reuters recently.
"For internal security reasons, there will be a continuing focus on Somalia and I do not foresee any significant change towards Eritrea," he said, referring to Ethiopia's arch-foe with whom it fought a decade-long border war.
But Ethiopia would be less willing to devote a lot of time and resources to problems further afield, Shinn said.
However, international rights groups say Meles was intolerant of dissent. Several opposition figures and journalists have been arrested under a 2009 anti-terrorism law.
State television said details of his funeral would be announced soon, the Horn of Africa country's first state burial in modern times.
Emperor Haile Selassie was laid to rest in 2000, 26 years after he was deposed. His body was found decades later beneath a palace lavatory in what forensic experts said were signs he had been murdered.
Another deposed leader, Mengistu Haile Mariam lives in exile in Zimbabwe.