The United States embassy in Kuala Lumpur was shut down today due to an unspecified security threat, and the police presence around the building was beefed up.

"The embassy will close effective today ... until further notice due to a security threat to the embassy," the embassy said in a statement.

US embassy spokeswoman Kathryn Taylor said the mission, which is on a main thoroughfare in the heart of Kuala Lumpur, was closed at 11:40am but would not specify the nature of the threat.

"Unfortunately I can't say at this time because it's something we're actively looking to," she said.

"The information applies specifically to the US embassy and does not apply to US citizens or private US interests in Malaysia as far as we're aware."

Police in the city district where the mission is located said they had increased the numbers of patrol cars around the embassy, as well as the numbers of officers patrolling there.

"The request from the US embassy to us is to increase our security around the US embassy," district police chief Hasnan Hassan told AFP . "It's an increase of about 20 percent in manpower all around the clock."

Hasnan said the embassy had not given police any indication of the nature of the threat. The increased security would be maintained "until the US embassy is happy that there is no more threat to it and then we will call it off", he said.

Taylor said the situation would be reassessed on Monday, when the embassy is officially closed due to the New Year public holiday, and a decision made on whether to reopen on Tuesday.

The US embassy here last shut down in September 2004, after it received a letter containing a suspicious powdery substance. Sections of the mission also closed in August 2004 due to similar deliveries.

Police later said the incidents were hoaxes aimed at frightening Americans.

The mission was also closed in 2002 on the first anniversary of the September 11 strikes on the United States.

Mission in Manila also closed

The US embassy in the Philippine capital Manila also declared a temporary closure of its public services earlier this month, due to a "plausible threat" to the mission.

Security threats against diplomatic missions happen frequently in Malaysia, although there have been no terrorist attacks on Malaysian soil.

The most recent incident was in October when a series of suspicious packages - containing liquids and threatening notes over the perceived mistreatment of Muslims - sparked scares at more than a dozen embassies and missions.

They were later found to contain only harmless substances.

Tight security at embassies here was breached in April 2004 when a group of enraged refugees burned down the Myanmar consulate.

In March that year, a small explosive device was thrown at the Australian High Commission from a speeding car, causing no injuries or damage.

The government said last month said that all militant suspects in Malaysia belonging to the Jemaah Islamiyah extremist network - blamed for many attacks in Asia - had been detained under its harsh Internal Security Act.

Malaysia is currently holding over 100 people in detention under the act.