Anti-terrorist specialists have been sent to embassies and missions around the world to determine how many are vulnerable and to decide what measures to take.
A specific warning was issued yesterday for American citizens in Lebanon to exercise the "highest level of caution" after the embassy in Beirut received intelligence that its compound may be the target of an attack similar to the twin bombings on 7 August of the US embassies in Kenya and Tanzania.
Last week the embassy in Kuwait warned Americans in the country that terrorists may be planning attacks there. The embassies in Ghana and Togo were also closed temporarily.
Officials are convinced that terrorists linked to Mr bin Laden were close last month to mounting an attack on the US embassy in Tirana, the capital of Albania.
There is anxiety in Washington that Mr bin Laden may be plotting assaults against the US in retaliation for August's missile strikes against his training camp in Afghanistan, as well as the air strike on a pharmaceutical plant in Sudan, which Washington described as punishment for the embassy bombings in East Africa that killed 253 and wounded more than 5,000.
Suggestions about bounties first surfaced in a Pakistan newspaper the day after the US missile strikes: it reported that Mr bin Laden was offering $10,000 for each American life. Persistent rumours of a price on American heads have not been confirmed by US intelligence.
A blanket warning from the State Department last Friday said: "Americans should maintain a very low profile, vary routes and times for all required travel and treat mail from unfamiliar sources with suspicion." Several US firms have issued similar instructions to executives overseas.
While none has been confirmed by US intelligence, rumours have swirled for days that Mr bin Laden has offered $10,000 for each American assassinated by his followers.
Embassy staff in Beirut said they had no specific intelligence about an attack, but nervousness was heightened by memories of April 1983, when, at the height of Lebanon's civil war, a suicide car bomber killed 62 people at the compound.
Meanwhile, apparent flaws in the security arrangements at the Nairobi embassy are before it was attacked is likely to spur controversy. The New York Times yesterday reported that the driver of the bomb car had easy access to parking next to the embassy, which was shared with a commercial bank next door. The area was protected by local guards, earning just $100 a month and patrolling unarmed. The security loophole had remained open in spite of warnings about it to Washington from the US ambassador, Prudence Bushnell. The State Department is preparing a request to Congress for some $3bn for a rapid construction programme for its embassies. If the funds are granted, it would mean that many of the embassies would be turned into virtual fortresses.Reuse content