The U.S. Embassy in the Saudi capital reopened Sunday after a temporary closure due to terror threats in the days after suicide attackers bombed Western housing compounds.

American consulates in the western port city of Jiddah (search) and the eastern city of Dhahran (search) also reopened Sunday.

The United States, Britain, Germany and Italy closed their embassies and consulates Tuesday after Saudi and U.S. officials said they had new intelligence pointing to the possibility that Usama bin Laden (search)'s Al Qaeda (search) group might launch fresh attacks in the United States or against American interests overseas.

Britain and Germany reopened their embassies and consulates on Saturday. The Italian Embassy also reopened Sunday.

A message on the U.S. Embassy hot line Saturday night urged Americans in the kingdom to continue to exercise "extreme caution and remain vigilant."

Security in Riyadh has been greatly increased since the May 12 suicide bombing attacks that killed 34 people -- including eight Americans, two Britons and nine attackers -- and injured nearly 200.

Saudi officials have detained about 100 people in a sweeping crackdown on extremists following the attacks; four men in custody are allegedly tied to Al Qaeda.

Also Sunday, Japanese Prime Minister Junichiro Koizumi arrived in Riyadh on his first visit ever to Saudi Arabia.

He was received by Crown Prince Abdullah and Defense Minister Prince Sultan and was expected to discuss various issues, including reconstructing Iraq, the Middle East peace process, the attacks in Riyadh and bilateral relations.