Britain on Thursday warned against nonessential travel to Kenya (search) and suspended its flights to and from the East African nation, after an Al Qaeda (search) suspect wanted in three terror attacks reportedly returned there. The United States also warned its citizens to postpone visits.

It was not immediately clear if the warnings were directly linked to the apparent return of Fazul Abdullah Mohammed (search), who is wanted in 1998 U.S. Embassy bombings and attacks on the Kenyan coast last November, and is on the FBI's list of most-wanted terrorists. But both the United States and Britain warned of new attacks.

Early Thursday, Kenyan authorities reported that they believe Mohammed had returned to the city of Mombasa from neighboring Somalia. Matthew Kabetu, head of Kenya's anti-terrorism unit, said Mohammed could be planning another attack and that police were searching for him.

Britain's Department for Transport said "the threat level to U.K. civil aviation interests in Kenya has increased to imminent," and suspended flights after 6 p.m. EDT.

It was not clear how many flights were affected. British Airways has one round-trip flight a day to Nairobi, which will be canceled indefinitely. Kenya Airways' seven flights a week from London to Kenya were not affected.

The U.S. State Department warning, issued late Wednesday, told Americans to defer nonessential travel to Kenya. It said the U.S. government had indications of terrorist threats against U.S. and Western interests, including civil aviation, and that the Kenyan government might not be able to prevent the attacks.

"Terrorist actions may include suicide operations, bombings, or kidnappings," the statement said. "U.S. citizens should be aware of the risk of indiscriminate attacks on civilian targets in public places including tourist sites, American commercial interests, and other sites where westerners are known to congregate."

A separate State Department travel warning said there is a credible threat of terrorist attacks throughout East Africa. It urged travelers to the region to review their plans.

The British Foreign Office also advised against nonessential travel to Kenya, including vacations. It advised Britons already in Kenya to keep a low profile and to be vigilant in public places. An estimated 1,200 Britons are currently on holiday in the east African country.

Kenyan National Security Minister Chris Murangaru accused Britain and the United States of overreacting, and said any talk of an imminent threat was "pure conjecture."

Murangaru said Kenya had information of a general threat in the region that had been known for some time. He said the reports of Mohammed's return had led to increased security, particularly around foreign embassies.

The FBI has indicted Mohammed in the 1998 U.S. Embassy bombings in Nairobi and Dar es Salaam, Tanzania, that killed 231 people, including 12 Americans. He is described as a slight man in his late 20s or early 30s and a computer expert who speaks many languages including French, Arabic and English.

A U.S. Embassy official in Nairobi said the United States "applauded Kenya's efforts to combat terrorism," but would not comment on Kabetu's claim that Mohammed could be planning another attack. The official spoke on condition of anonymity.

Mohammed fled to neighboring Somalia after a Nov. 28 bombing at a hotel near the port city of Mombasa that killed 11 Kenyans and three Israeli tourists. Minutes before the bombing, unidentified assailants fired two missiles at a charter aircraft with Israeli tourists leaving Mombasa, but missed.

Kabetu said Mohammed is also suspected of helping mastermind the Nov. 28 attacks.

In Britain, Magnus Ranstorp, a terrorism expert at the Center for Terrorism and Political Violence at St. Andrews University in Scotland, said the British government's move on Thursday was drastic but sensible.

"This has never happened before to my knowledge. If they did not take precautions it could be catastrophic, particularly given what happened in Mombasa," he said.

The State Department travel warning said the threat to aircraft by terrorists using shoulder-fired missiles continues in Kenya and includes Nairobi.

Mohammed is reported to have trained in Afghanistan with Usama bin Laden. The State Department says supporters of Al Qaeda and other extremists are active in the region.

Al Qaeda has been blamed for both the 1998 and Nov. 28 attacks.

Kenya shares a long and porous border with Somalia, a Muslim nation that has not had an effective government since 1991. U.S. officials say Somalia may have been a haven for terrorists since the Sept. 11 attacks.