President Clinton: "Co-ordinated attack"

He said that the US was sending counter-terrorism experts and medical teams to the region.

A team of US marines is also flying to the region to bolster security along with FBI agents.

"These acts of terrorist violence are abhorrent, they are inhuman," Mr Clinton said at the White House press conference.

"We will use all the means at our disposal to bring those responsible to justice," he added.

Mr Clinton said flags at all US government buildings would be flown at half-mast as a mark of respect to the victims.

'Terrorists' blamed

The State Department described the explosions as being the work of terrorists - but said it was still unclear who was responsible.

A spokesman said the embassies involved had not been given any indication that they were under threat.

Security has now been stepped-up at all US installations in Africa.

Investigation underway

Bill Richardson: "We will not tolerate attacks"

Situation rooms have been set up at both the White House and the State Department.

Officials are trying to find out the number of casualties and determine who might have been responsible for the blasts.

US spokesman Bill Richardson said Washington was on friendly terms with both East African nations.

Richardson: "good security"

"These are countries we have very good relations with," he added.

"We are very concerned however if our people, our embassies, have been targeted. We are not going to tolerate that.

"But it's just too early to tell who's responsible. We are monitoring the situation very closely."

Mr Richardson added that he had visited both embassies and had been impressed with security.

African help

South Africa's air force is flying a rescue mission to Nairobi, at the request of the US, to evacuate survivors to hospital for treatment.

Lieutenant-Colonel Laverne Machine said a medical crew, including a military surgical team, would be on board to aid the evacuation mission.

Casualties would be flown to an army hospital in Pretoria, she added.

US Secretary of State Madeleine Albright was reported to be cutting short a visit to Italy following the blasts.