Updated

A self-proclaimed "anti-American" group is threatening to carry out terrorist attacks against diplomatic compounds, airlines and public transportation systems in eight U.S. allies, several of which have sent troops to Iraq (search), a South Korean official said Thursday.

The group, called the "Yello-Red Overseas Organization," warned in a one-page letter sent to the South Korean Embassy in Thailand (search) that it will launch the attacks through April 30, embassy spokesman Ryoo Jung-young told The Associated Press.

The group described itself as "anti-American" and threatened to attack diplomatic compounds, airlines and public transportation systems in South Korea, Japan, Thailand, the Philippines, Singapore, Australia, Kuwait and Pakistan. Several of these countries have sent troops to Iraq.

Ryoo said it was the first time South Korean authorities had heard of the group and were investigating the threat's credibility. The letter was received Wednesday.

The South Korean Foreign Ministry in Seoul said it had not notified other nations on the list but that it had confirmed that the Pakistani Embassy in Bangkok had also received a similar letter, an official said on condition of anonymity. South Korean diplomatic missions worldwide were alerted to the threat.

South Korea plans to send 3,000 more troops to Iraq, which would make it the biggest coalition partner behind the United States and Britain.

The deployment, pledged earlier this year, was put on hold amid concerns it would involve combat operations in violation of a parliamentary mandate for peacekeeping.

Last week, Philippine President Gloria Macapagal Arroyo said mounting violence in Iraq has prompted her government to study whether to withdraw its nearly 100 troops from the Mideast nation.

Japan and Australia, which also have troops in Iraq, have pledge to keep them there.