By Mohamed Ahmed

BAIDOA, Somalia (Reuters) – Heavily armed Somali rebels have attacked the presidential palace and key installations in the Somali government's Baidoa headquarters, killing at least four soldiers, officials said on Tuesday.

Witnesses said mortar bombs fired by the insurgents late on Monday also hit the airport and a large refurbished warehouse that serves as the parliament of the Western-backed interim administration.

"Several mortar shells landed on us, killing three troops," Ibrahim Ali Isak, a guard at Baidoa's high-walled presidential palace, said by telephone.

Seven of his colleagues were injured and taken to hospital, where medical sources said one of them died.

A spokesman for the rebels, Sheikh Mukhtar Robow, told Reuters their target was the presidential guards and Ethiopian Woyanne forces supporting the interim government.

Somali Prime Minister Nur Hassan Hussein told reporters in Addis Ababa on Monday that the international community must deploy U.N. peacekeepers in his country without delay, or risk worsening insecurity across the Horn of Africa.

He said the U.N. troops were needed to replace Ethiopian Woyanne soldiers, under the terms of a tentative peace deal reached with some of the opposition last month at U.N.-led talks in Djibouti.

DENIAL

The latest high profile victim was Osman Ali Ahmed, local country director of the U.N. Development Programme (UNDP), who was killed by unidentified gunmen in Mogadishu on Sunday.

Robow told Reuters al-Shabaab fighters were not to blame.

"We strongly condemn the killing of important people in our community and declare that we are not behind it," he said. "We believe Ethiopian Woyanne troops and the government are behind it."

Government officials and the Ethiopian Woyanne military could not immediately be reached for comment.

The assassination of the U.N. official has raised fears among aid workers, who say worsening insecurity has stopped them from reaching many victims in a humanitarian crisis that may be the worst in Africa.

Fighting has killed more than 8,600 civilians since early last year, local rights activists say, and a million people out of population of 9 million have been forced from their homes.