Emergency services rushed to the tightly-guarded US embassy in Kuala Lumpur today after a powder which police said could be anthrax was found in a letter.

"The envelope containing an unidentified substance was opened by an embassy employee this morning and the Malaysian police Hazmat (hazardous materials) unit was called in to inspect it," an embassy spokesperson told AFP .

"At this point all the appropriate actions are being taken. The substance is being tested." The embassy spokesperson said staff had not been evacuated and continued to work as usual.

The incident comes just days after an anthrax scare at the US embassy in Sri Lanka last week turned out to be a hoax, with tests on a powdery substance received in the mail proving negative.

Police spokesman Aman Hussain told reporters at the scene in Kuala Lumpur: "At the moment this powder, according to Hazmat, may be anthrax". It would be sent to a laboratory for tests.

Three people who had been exposed to the powder were "under quarantine" in the embassy while being checked by doctors, he said.

Series of threats

The letter was believed to have been posted locally and contained a message, Aman said, without disclosing the contents of the message.

Half-a-dozen police cars, a fire brigade vehicle and an ambulance raced to the embassy in the centre of the capital of this mainly-Muslim nation after the alert was raised.

The scare follows a series of threats against foreign missions here, including one in April which warned Japan to pull its troops out of Iraq.

Malaysia's government strongly opposed the US-led invasion of Iraq, but has recently offered to help in its reconstruction.

More than 80 alleged Islamic militants have been detained in recent years, many of them suspected members of the regional Jemaah Islamiah terrorist group responsible for a series of bombings in neighbouring Indonesia, but there have been no terror attacks on Malaysian soil.

Tight security at embassies in Malaysia was breached in April when a group of enraged refugees burned down the Burmese consulate, while on March 30 a small explosive device was thrown at the Australian High Commission from a speeding car, causing no injuries or damage.