BANGKOK - RIOT police have fled a checkpoint near Bangkok's main international airport after coming under attack by several hundred anti-government protesters.

About 150 police at the checkpoint jumped into their vehicles and drove away when they saw a convoy of protesters speeding toward them.

The checkpoint was about a mile (2 kilometres) from Suvarnabhumi airport. Protesters have occupied the airport since late Tuesday, forcing the halt of all flights.

Some of the protesters carried guns. Many were armed with metal rods and hit the police vehicles as they drove off, smashing windshields and throwing what appeared to be firecrackers at police.

Police earlier on Saturday built a massive cordon around anti-government protesters occupying Thailand's main airport on Saturday, raising fears of an imminent confrontation in a standoff that has disrupted the country's economy and the travel industry worldwide.

About 2,000 policemen were deployed around Suvarnabhumi international airport, where protesters calling themselves the People's Alliance for Democracy have camped out since late Tuesday, forcing the halt of all flights.

The protesters also have occupied Bangkok's domestic airport and the prime minister's office compound, virtually paralyzing the government in their campaign to force its resignation.

The confrontation, severing the capital from civilian air traffic, has taken a heavy toll on Thailand's economy and reputation. According to Thai media reports some 100,000 tourists are stranded, and schedules of airlines around the world have been disrupted.

So far security forces have only issued a warning to the protesters to leave and refrained from using force. The protesters say they will not leave until the government of Prime Minister Somchai Wongsawat resigns.

But it appears the government's patience is wearing thin.

'The police will issue another warning to protesters to leave the two airports. The language in the warning will be stronger than the first one,' said a police spokesman, Maj. Gen. Amnuay Nimmano.

He said if the protesters do not leave, a deadline will be issued 'in the third warning - the last one before we take action'.

The 2,000 policeman at Suvarnabhumi were deployed at all exit and entry points around the airport, said police Major General Rachandra Ruenkamon, the deputy chief of operations in the area.

One checkpoint on the main highway leading to the airport on Bangkok's outskirts was manned by about 400 policemen accompanied by about 20 navy sailors armed with M-16 rifles.

The roadblocks were meant to prevent more protesters from joining thousands of others inside the terminal building.

About 50 soldiers guarded the maintenance facility of the airport, a few kilometers (miles) away from the main complex.

Several airlines are flying rescue flights to the U-Tapao naval airport, 140 kilometres south of Bangkok, to evacuate stranded passengers. But the small airport is overwhelmed by the load, unable to process thousands of travelers quickly.

Among those stranded are about 3,000 Chinese tourists who will be flown out on special flights by four Chinese airlines beginning Saturday, China's Xinhua News Agency reported. It said the Hong Kong government has also arranged two Cathay Pacific flights to help stranded passengers.

Several groups around the world have canceled planned tours, and 88 aircraft, many of them belonging to foreign airlines, are parked at Suvarnabhumi unable to take off.

The Federation of Thai Industries estimates the cost of lost trade due to the airport shutdowns at US$57 million (S$86 million) to US$85 million a day.

Thailand's central bank said the number of tourist arrivals is likely to fall by 40 per cent next year if the airport shutdown drags on until the end of December. It said the tourism industry, a key component of the Thai economy, is expected to lose US$4.28 billion, equal to 1.5 percent of the gross domestic product.

With international repercussions obvious, the European Union and the United States urged the protesters to end their siege.

The People's Alliance for Democracy accuses the government of being a puppet of former Prime Minister Thaksin Shinawatra, who was ousted by a 2006 military coup and fled overseas to escape corruption charges.

Prime Minister Somchai, who is Thaksin's brother-in-law, is now operating the government out of the northern city of Chiang Mai, blocked out of his office in Bangkok.

Tension rose further on Saturday after a pro-government group expressed frustration at the continuing standoff and called for an indefinite sit-in starting Sunday in central Bangkok.

'We are calling for our supporters nationwide to come out (for the rally). They have been told to bring their clothes and food because we will be here long,' said Viphutalaeng Pattanaphumethai, a leader of the group, which in the past has clashed with the alliance.

Its members wear red shirts to distinguish themselves from the alliance, whose supporters wear yellow.

At the Suvarnabhumi airport, Associated Press reporters saw one policeman being grabbed on Saturday at a checkpoint by three protesters, forcibly put in a vehicle, and driven away toward areas controlled by the demonstrators. His whereabouts remained unclear. -- AP

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