The police on today said they regarded a letter containing a white powder sent to the US embassy here with a threat to blow up the mission as a hoax aimed at frightening Americans.

City criminal investigation chief Aziz Bulat told AFP the envelope was sent on Monday by a group that identified itself as Jemaah Muhajirrin Muhamad.

"It is an unheard group. In the letter they threaten to blow up the US embassy and demanded the US pulls its forces out of Iraq," Aziz said.

"We are investigating the matter but we believe it is a hoax. It is just to scare the Americans," he said.

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

Aziz said authorities were testing the white powder, adding that the results should be known by the latest tomorrow.

Two men and a woman working at the embassy, all US citizens who had been exposed to the powder, were back at work after being checked by doctors, an embassy spokesman said yesterday.

Aziz said Malaysia was a safe country and foreigners should not be alarmed.

"We would like to assure Americans that Malaysia is safe," he said.

Anthrax scare

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.

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.