'These acts of terrorist violence are abhorrent, they are inhuman,' he said in Washington, vowing: 'We will use all the means at our disposal to bring those responsible to justice no matter what or how long it takes.' American and British diplomatic missions were put on alert.
Within hours of the explosions at the embassies in Nairobi and Dar-es-Salaam, intelligence agents and other experts were en route to Nairobi from the United States and from American installations in 'other countries', the FBI said.
And last night a special task force was flying to Nairobi from Andrews Air Force base near Washington, the Pentagon said. The team included FBI investigators and experts in explosives, terrorism and communications. A Marine Corps security squad was also being sent.
A second task force was being assembled to go to Tanzania.
There was no warning and no group claimed responsibility for the attacks on the two lightly guarded embassy buildings, according to the state department in Washington. But there was speculation that Middle Eastern Islamic extremists were involved.
In the Kenyan capital - site of the deadlier of the two attacks, which both occurred soon after 10.30am local time - an Arabic-speaking man was reported to have been taken into custody by police in connection with the bombing. An Associated Press photographer saw him being detained.
Eighty-one people died in the two cities, most of them local residents. In Nairobi, there were still dead and living in the debris of the US embassy and an adjacent building last night.
At least eight Americans were among the 74 dead in Kenya and six were missing. The ambassador, Prudence Bushnell, was found covered in blood after the blast - one of more than 1,600 wounded - but helped direct the rescue after being treated.
Two buildings took the full force of the main blast from a parked van - the US embassy and, behind it, Ufundi Co-op House, which contains a secretarial college and offices. Ufundi House collapsed floor by floor, crushing its occupants. The embassy's reinforced five-storey structure survived but its rear-facing rooms were reduced to blackened shells.
Office workers, cut by glass, streamed away from the scene and a trail of blood led back to the embassy. Six buses lay gutted nearby, the driver of one thrown, dead, halfway through his window.
A preacher, Julius Koiyet, said that before the big blast, he saw three men throw a tin container about 12 inches long towards the embassy. It bounced on to a nearby building where it blew up, he said.
In Dar-es-Salaam, the other soft target to be hit, about two thirds of the American embassy was destroyed by a car bomb that exploded in the embassy's car park, in a residential area north of the city centre near the Indian Ocean. Police said that, as well as the seven known dead - five of whom were local embassy employees - 72 people were injured.
Medical supplies and military surgeons were being flown in last night from the Washington area, from America's Ramstein Air Base in southern Germany, and from South Africa.
Appearing on national television to extend his sympathies to the families of the victims, the Kenyan president, Daniel arap Moi, expressed disbelief that such terrorist acts had happened in Kenya . ' Kenya is not at war with any other country and we don't deserve this kind of tragedy.' Kenya is heavily dependent on tourism earnings, which the explosion is bound to hit.
Suspicions were focused on the Egyptian fundamentalist movement, Islamic Jihad, which earlier this week issued a threat against the US for what the group claimed was the CIA's role in helping extradite four of its activists from Albania to Cairo.
'We warn the Americans that their message has reached us,' an Islamic Jihad communique said. 'The response that we want them to read with care is nigh, for we shall write it, God willing, in a language which they understand.'
Another possible perpetrator was Osama bin Laden, the exiled scion of an enormously wealthy Saudi merchant family. Until recently at least, he was based in Afghanistan.
The scene in Nairobi after the blasts was chaos. Smoke rose high in the air and emergency services battled with each other and with civilians to get to the survivors.
Gesturing at dazed and bloody survivors crumpled on sidewalks and in the road, a local man, Wilberforce Mariaria, asked: 'How can someone think of doing this kind of thing?'
