The U.S. Embassy in Malaysia said Tuesday it had received a "credible and specific threat" to security and would close until further notice.
"Because of a credible and specific threat to the security of the U.S. Embassy in Kuala Lumpur, the embassy will be closed Wednesday, Sept. 11 to review its security posture," the embassy said in a statement.
It was the second embassy in the region to be ordered closed because of terrorist fears on the eve of the anniversary of the Sept. 11 attacks. The U.S. Embassy in Jakarta, Indonesia, closed earlier Tuesday.
The U.S. Embassy in Cambodia was also closed as a precaution, and U.S. troops in the Philippines were on heightened alert.
Malaysia police were called to provide extra security at the embassy late Tuesday after officials there were alerted to the threat.
The embassy warned U.S. citizens in Malaysia to be "extremely cautious" in coming days.
"They should maintain a high level of vigilance and take appropriate steps to reduce their vulnerability and maintain a low profile," a statement said
Malaysia, a mostly Muslim country of 23 million people, has become a focus of the investigation into the Sept. 11 attacks. It has detained scores of Islamic militant suspects accused of belonging to an extremist network in Southeast Asia.
Prime Minister Mahathir Mohamad is a key U.S. ally in the region in the international fight against terrorism, and Malaysians have generally decried the Sept. 11 attacks.
But many oppose U.S.-led military action against Muslims, and a fundamentalist minority has strong sympathies for Islamic extremists, including Osama bin Laden.
Among the militant suspects detained by authorities is a former Malaysian army captain who officials say let senior al-Qaida operatives, including two of the Sept. 11 hijackers, use his apartment for a meeting in January 2000.
The former captain, Yazid Sufaat, is also alleged to have bought four tons of a chemical compound that officials believe was intended for use in a bombing of the U.S. Embassy in neighboring Singapore. The plot was foiled after Malaysian and Singapore police made dozens of arrests in December.