Thailand has told three officials from the Iraqi Embassy to leave the country because they threatened national security.
Security is being stepped up across the region
Prime Minister Thaksin Shinawatra said the expulsions were the result of cooperation between Thai and US intelligence agencies.
"Three diplomats have been expelled due to the nature of their
work involving intelligence, which was a likely threat to national
security," the prime minister told reporters.
Thailand appeared to be acting partly in response to a US alert earlier this month that Iraqi agents were preparing to attack American interests in up to 60 countries.
The Thai move came as Asian countries braced for possible terrorist attack and violent domestic protests in the event of a US-led war in Iraq.
The militants and terrorists would obviously want to exploit the situation and even the moderate Muslims will be very angry
Malaysian Acting Prime Minister, Abdullah Ahmad Badawi
South Korea, which on Wednesday backed a US-led attack on Iraq and said it might send non-combatant troops to help, said it would step up
security at US military bases and other interests.
Security will be stepped up at foreign embassies and
diplomats' residences, the National Police
The Philippines government deployed hundreds of extra troops to airports and other sites on Tuesday.
Police in Indonesia said that they were anticipating violent protests from radical Islamic groups.
And ministers from the Association of Southeast Asian Nations (Asean), cutting short a meeting in Malaysia because of expected war, said they were worried that Western tourists and businesses could become targets for terrorists sympathetic to Iraq.
Ong Keng Yong, Asean secretary general, was particularly worried about the threat to Western targets in the region.
"The one place that has a lot of Western presence, where people can still move in and out freely, is Southeast Asia," he said.
"Naturally the terrorists will want to see how they can attack any of these targets."
The British Embassy in Jakarta advised its citizens to avoid night clubs and bars in Indonesia.
"We continue to receive information that indicates
extremists may be planning additional attacks targeting Western
interests and may take advantage of heightened tensions over
Iraq to launch an attack," the embassy said in a statement.
The Philippines went on high alert against reprisal attacks on Tuesday.
Extra troops were deployed at airports, embassies and churches.
"We must be pro-active against collateral terrorist attacks," said President Gloria Arroyo, speaking on national radio.
President Arroyo has been a staunch supporter of President Bush.
Military officials said that they were worried that Muslim rebels fighting in the south of the country might target the capital Manila if America invaded Iraq.
In Malaysia, Acting Prime Minister Abdullah Ahmad Badawi warned that war would "put the governments of Islamic countries under severe strain".
"The militants and terrorist would obviously want to exploit the situation and even the moderate Muslims will be very angry", he told the AFP news agency.
Indonesia, home to the world's largest Muslim population, is bracing itself both for the terrorist threat and violent domestic protest.
Indonesian police said that they have drawn up a security plan to control protestors, prevent attacks on Westerners and foil any terrorist threat.