The US embassy was shut indefinitely today after it received a letter containing a suspicious powdery substance, its second security scare in two weeks.

"The US embassy in Kuala Lumpur will be closed until further notice pending test results on a suspicious substance that was received on Sept 2," it said in a statement.

An embassy spokesman told AFP that the letter containing "suspicious powder" was opened by a staff member this morning. The Malaysian police hazardous materials unit had been called in to inspect it, he said.

The incident was the second since Aug 16 when sections of the embassy were closed briefly after receiving a letter containing a white powder with a threat to blow up the mission. Police later said it was a hoax aimed at frightening Americans.

Series of threats

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 Islamiyah militant group responsible for a series of bombings in neighbouring Indonesia.

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 Myanmar 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.