Nairobi was on a high state of alert yesterday following a warning by the US Embassy of a new terrorist threat.

And two buildings in the Central Business District were evacuated when anonymous callers warned of bombs. The warnings turned out to be a hoax.

The new fears come ahead of a visit by the US Health Secretary Mr Tommy Thompson to Nairobi later in the week.

Barclays Plaza was evacuated for four hours after the KLM airline office received a phone call saying there was a bomb in the building, Mr Patrick Kinyua, the head of security for the building, said.

Until recently, the building housed the US Embassy Public Affairs office.

And a Barclays branch office, also in the CBD, was also evacuated for several hours when the manager received a similar threat.

The Minister for Tourism and Information, Mr Raphael Tuju, confirmed the Government had received information about a threat to two downtown hotels in Nairobi.

"We are evaluating it and taking the necessary action," he said. Tuju said it would not be appropriate to comment further. "We have had similar kind of warnings in the past but I don’t want to go into the details," he said.

The Government sent armed General Service Unit personnel to guard the buildings.

The US Embassy sent warnings to all American citizens to stay away from the CBD following what it termed an uncorroborated and anonymous report of a potential terrorist attack.

The US Government recently received an anonymous warning detailing terrorist threats aimed at American and Western interests in downtown Nairobi.

" ... the timing of the threat is within the next several days," the embassy said in a statement.

The United Nations also warned its employees to keep off the City centre yesterday and today.

The US embassy spokesman, Mr Peter Claussen, said American authorities received an anonymous tip detailing the terrorist threats on Monday.

Embassy officials have already shared that information with Kenyan authorities and have been assured the necessary steps are being taken to counter the threat.

A high-level security meeting was hurriedly convened at Vigilance House in the afternoon to validate the information regarding the reports of a planned terror attack in the city.

Senior police officers including the officer Commanding Anti-Terrorism Unit, Mr Mathew Kabetu, his deputy Mr Kaua Mbijjiwe and the Nairobi Provincial Police Officer, Mr Jonathan Koskei, met from 2.30 pm to discuss the alert.

A senior police source, while confirming that the was information of a possible terror attack on hotels, vital installations and embassies, said all sites had been checked and no unusual discoveries had been made.

He added that all the installations and premises were currently being guarded.

He noted that terrorists do not warn or reveal where they intend to strike, but instead claim responsibility after the act.

Kenya has been attacked by terrorists twice. On August 7, 1998, the US embassy was destroyed and 219 people killed in a terrorist bomb attack. In November 2002, a car bomb blew up outside the Paradise Hotel in Kikambala, north of Mombasa, killing 15 people, including three Israeli tourists.