The United States has temporarily closed six of its embassies in Africa, and Britain has shut four, amid reported fears of a terrorist attack like last year's bombings of the U.S. missions in Kenya and Tanzania.

The State Department shut its embassies Thursday in Senegal, Gambia, Liberia, Togo, Namibia and Madagascar. Today, Britain closed its missions in the same countries except for Liberia and Togo, where the British are not in residence.

Spokesman James P. Rubin said in Washington that the State Department ordered the closures "as a precautionary, prudent measure" after receiving "information suggesting suspicious individuals were surveying the sites." Rubin said the State Department will assess over the weekend whether to keep the six embassies closed next week.

Neither government identified the source of the threat, but U.S. officials said it appeared to be the network of exiled Saudi dissident Osama bin Laden, accused by Washington of masterminding last August's bombings, which killed more than 200 people. Since then, U.S. embassies in Africa have tightened security and Washington has continued to treat bin Laden as the principal anti-U.S. terrorist threat abroad.

On June 10, the State Department issued a "worldwide caution" against terrorist threats that focused mainly on bin Laden. And the FBI this month added bin Laden to its 10 Most Wanted list. In response to questions on bin Laden, Rubin said today that "we have seen a pattern of activity indicating continued planning for terrorist attacks by members of Osama bin Laden's network. And we take reporting of such threats seriously."

U.S. officials said this month that they had seen signs that a network loyal to bin Laden was in the advanced stages of planning for a new attack against an unspecified U.S. target, ABC News reported last week. On June 10, a television station in the Persian Gulf state of Qatar broadcast an interview with bin Laden in which he repeated his previous calls for a holy war against the United States.

Bin Laden -- an Islamic militant and opponent of the Saudi government -- is believed to be in Afghanistan. At the time of last year's bombings, he was a "guest" of the Taliban militia, which controls most of Afghanistan, but Taliban leaders now claim not to know bin Laden's whereabouts.

The State Department's order shut all U.S. government offices in the six countries -- including those of the Peace Corps and the U.S. Agency for International Development -- but essential embassy personnel were still at work and emergency services for American citizens were still being provided, U.S. diplomats in West Africa said.

Peace Corps volunteers, who serve in all six countries except Liberia, were otherwise unaffected, a Peace Corps spokesman said.

While all U.S. diplomatic missions are keeping security tight, spokesmen at several embassies in West Africa said they have noted no explicit threat toward Americans. The embassy in Dakar, Senegal, had noted no surveillance, "nothing unusual, no particular threat," said Van Swengsouk, its spokesman.

"The State Department sent us instructions to close, so we did. They didn't tell us what the security threat was," said James O'Callaghan, spokesman of the embassy in Lome, Togo. "They said they'll reevaluate on Sunday and we hope that will be the end of it, because this is a real pain."

A British Foreign Office spokesman in London declined to specify whether closure of its embassies was prompted by the U.S. decision or by any threat from bin Laden. "We do maintain close contacts with the Americans on security matters . . . but we never comment on any security or intelligence matter," said the spokesman, quoted by the Reuters news agency.

Bin Laden has not issued any explicit public threats against Britain, but a court in London is considering a U.S. request that Britain extradite a former bin Laden aide, Khalid Fawwaz, who was indicted in New York this month in connection with the August bombings.

Ever since vehicles crammed with explosives blew up outside the U.S. embassies in Kenya and Tanzania last August, security has been tightened at many U.S. missions on this continent. U.S. embassies in much of Africa were shut down for two days in December after U.S. airstrikes against Iraq. The embassy in Uganda also has closed several times for security alerts.

In Senegal, Togo, Mali, Ivory Coast and many other countries, whole city blocks around the U.S. embassies have been closed to traffic. Here in Abidjan, roadblocks sealing off the U.S. Embassy cut road access to Ivory Coast's Supreme Court as well, and snarl access or parking for nearby U.N. offices and government ministries.

Some of the embassies closed today are seen as physically vulnerable. While U.S. rules require embassies to be set back from public streets, many older embassies have no such protection. The embassy in Lome, at a narrow intersection of two dirt streets, barely has a concrete curb between it and the street.

Staff writer Thomas W. Lippman in Washington contributed to this report.

Embassies Closed in Africa

Banjul, Gambia

Dakar, Senegal

Monrovia, Liberia

Lome, Togo

Windhoek, Namibia

Antananarivo, Madagascar