* Meles Zenawi in power since 1991
* Diplomats say he is receiving treatment in Brussels
* Opposition groups say he is seriously ill, dead
By Aaron Maasho
ADDIS ABABA, July 18 (Reuters) - Ethiopian Prime Minister Meles Zenawi has been treated for an illness and is "in good condition", a government spokesman said on Wednesday, amid rising speculation about the health of a man in power for two decades in a poor, violent corner of Africa.
Rumours that he is seriously ill have been rife since the former guerrilla leader, in power since ousting Mengistu Haile Mariam's military junta in 1991, failed to attend an African Union summit in Addis Ababa over the weekend.
Meles, 57, has won praise in the West for his country's solid economic growth and poverty reduction, but rights groups have criticised his government's repression of dissent and poor record on human rights and freedom of expression.
Washington's main ally in the Horn of Africa, Ethiopia has volatile Somalia and Sudan as neighbours along with arch-foe Eritrea, and speculation about Meles' health after some weeks' absence from public view has stirred debate about who might replace him.
Diplomats in the Ethiopian capital say Meles is receiving treatment in Brussels for an undisclosed illness. Other sources have said he was treated in Germany, while some opposition groups say he has a life-threatening ailment or has died.
"He has received treatment and is in good condition," government spokesman Bereket Simon told Reuters. He declined to say what Meles' illness was and where he is receiving treatment.
An Ethiopian diplomat in Europe referred to the rumours about his health as "scare-mongering".
"His condition is stable and he is on the mend and he will be back to work soon," the diplomat said. "He has had hospital treatment. There is no serious threat to his health."
Meles, known for his sharp tongue and sarcastic quips, has said he intends to step down in 2015 at the end of his fourth five-year term as premier.
Violence tore through Addis Ababa when Meles's ruling Ethiopian People's Revolutionary Democratic Front (EPRDF) declared it had won disputed elections in 2005.
Security forces killed 193 protesters, and 7 policemen also died in violence that damaged the standing of one of the world's biggest aid recipients.
The opposition also alleged that the country's last polls, two years ago, were fraudulent.
The EPRDF has also come under fire for its arrests of journalists, with watchdogs accusing the government of cracking down on free speech under the guise of national security.
Addis Ababa dismisses the claims.
Twenty Ethiopians, including a prominent blogger, journalists and opposition figures, were jailed last Friday for between eight years and life for conspiring with rebels to topple the government, sentences whose severity was condemned by EU foreign policy chief Catherine Ashton and rights groups.