ADDIS ABABA — World leaders on Tuesday mourned the death of Ethiopian Prime Minister Meles Zenawi with high praise after the strongman's more than two decades in power and despite a checkered human rights' record. Meles, who held tight control over this East African country but was a major US counter-terrorism ally, died of an undisclosed illness after not being seen in public for weeks, Ethiopian authorities announced Tuesday. He was 57. Meles died Monday just before midnight after contracting an infection, state TV said. His death leaves a major power gap in the Horn of Africa. Ethiopia has played a key role in the fortunes of many of its neighbors, as well as host to the African Union headquarters in Addis Ababa. Kenyan President Mwai Kibaki called Meles a “pragmatic and visionary” leader who helped stabilise his country and placed it on the path of economic growth, adding that his death is a “devastating loss”. South African President Jacob Zuma praised Meles as “a strong leader, not only for his country but on the African continent” and the Horn of Africa in particular. “It is an absolute tragedy for Africa and the people of Ethiopia to mourn such an exceptional leader who contributed as an active role-player in various continental and global initiatives, especially in playing host to the African Union,” Zuma said in a statement. Hailemariam Desalegn, who was appointed deputy prime minister and minister of foreign affairs in 2010, became acting prime minister and will be sworn in as prime minister after an emergency meeting of parliament, said Bereket Simon, the communications minister. Parliament is controlled by Meles' ruling party and governing coalition, ensuring Hailemariam will be approved. No new elections will be scheduled, Bereket said. Bereket did not say where Meles died, only that he was abroad for medical treatment. Officials had expected Meles to return to Ethiopia but a sudden complication reversed what had been a good recovery, he said. A European Union spokesman said that Meles died in Brussels. Meles hadn't been seen in public for about two months. In mid-July, after Meles did not attend a meeting of heads of state of the African Union in Addis Ababa, Ethiopia's capital, speculation increased that his health problems were serious. Ethiopian officials gave no details and said the prime minister was in “very good” health and would return to office soon, but international officials said quietly it was unlikely he would recover. State TV on Tuesday showed pictures of Meles as classical music played in the background. Simon called the death shocking and devastating. The country's council of ministers declared a national day of mourning. Opponents of Meles accuse him of killing and jailing opposition members and of rigging elections. Ethiopia's Somalia community in particular has suffered under Meles, who won his last election in 2010 with a reported 99 percent of the vote. Jose Manuel Barroso, the president of the European Commission, offered his condolences to the Ethiopian people, praising Meles' development work and calling him “a respected African leader.” Born on May 8, 1955, Meles became president in 1991 after helping to oust Mengistu Haile Mariam's Communist military junta, which was responsible for hundreds of thousands of Ethiopian deaths. Meles became prime minister in 1995, a position that is both the head of the federal government and armed forces. State TV said funeral arrangements would be announced soon. — AP