Ms Anchalee Paireerak said the PAD would maintain a presence though its 'security guards' at Government House, which it overran in August, but would not be running a round-the-clock protest at the site, which has come under regular grenade attack.

'Everything has been moved to Suvarnabhumi and Don Muang,' she said, referring to the two airports.

The anti-government protesters reinforced their siege of Bangkok's two airports on Monday as the politically paralyzed country struggled with more than 300,000 stranded travelers.

In a switch of tactics, the People's Alliance for Democracy said demonstrators will end their more than three-month sit-in at the prime minister's office compound and join compatriots at the airports, which they seized last week in their push to oust the government. That action severed all civilian flights in and out of the capital.

Airlines, meanwhile, were flying dozens of empty planes out of Bangkok's international airport.

Some 30 planes had been flown out starting on Sunday and an additional 50 were to be moved later on Monday, some to protest-free airports elsewhere in Thailand so that stranded tourists, businesspeople and others can fly out of the country, said Serirat Prasutanont, acting director of the Airports Authority of Thailand.

The loss of international air links over the past week has forced thousands to cancel their vacations during peak tourist season, halted vital postal air services and stopped the arrival of everything from specialized medicines to raw fish for Bangkok's Japanese restaurants.

Neither the army nor Thailand's revered king has stepped in to resolve the crisis - or offered the firm backing that Prime Minister Somchai Wongsawat needs to resolve the leadership vacuum.

The crisis escalated on Sunday when some 10,000 pro-government activists converged on Bangkok to counter the anti-government protesters who have forced the prime minister to run the country from the northern city of Chiang Mai.

Explosions on Sunday targeting the anti-government protesters injured at least 51 people, officials said, with blasts hitting the prime minister's compound and a road near the occupied domestic airport. No one claimed responsibility for Sunday's blasts, but the alliance blamed the government.

Alliance leader Chamlong Srimuang called on protesters who have occupied the prime minister's compound since Aug 26 to 'move to the airports to support our people there.'

The move did not represent a softening of the protest group's stance nor was it clear whether the occupation of the compound was entirely over. Mr Chamlong told supporters they should move because it was not safe to remain at the compound, which has been attacked several times by grenades fired by unknown assailants.

King Bhumibol Adulyadej, who has intervened to resolve several political crises over the past four decades, is scheduled to deliver a much-anticipated speech on Thursday, the eve of his 81st birthday.

But whether he will actually move to resolve the paralysing situation is uncertain.

The Constitutional Court also is to rule soon on whether three parties in the governing coalition, including Mr Somchai's People's Power Party, committed electoral fraud. Closing arguments from the defendants will be heard Tuesday.

If found guilty, the parties would be dissolved immediately and executive members including Somchai could be barred from politics for five years. Whether this would satisfy the anti-government protesters is uncertain.

The Foreign Ministry planned to propose on Tuesday the postponement of the annual summit of the Association of Southeast Asian Nations, scheduled for mid-December in Thailand, ministry spokesman Thani Thongpakdee told The Associated Press.

The alliance says it will not give up until Mr Somchai resigns, accusing him of being a puppet of ousted Prime Minister Thaksin Shinawatra, the alliance's original target. Thaksin, who is Somchai's brother-in-law, was deposed in a 2006 military coup and has fled the country to escape corruption charges.

Alliance protesters managed to shut down Suvarnabhumi international airport last Tuesday and domestic Don Muang airport two days later, stranding scores of planes.

Mr Kongrit Hiranyakit, head of the Tourism Council of Thailand, said over 300,000 travelers were stranded in Thailand, with 35,000 to 45,000 being added to that number each day the airports remain closed. Thousands of others trying to enter Thailand from around the world are also in a holding pattern.

Some countries evacuated nationals by land. The Australian Embassy was helping stranded tourists travel by buses to the southern resort island of Phuket, where air traffic has not been disrupted, for flights to Australia.

'This is my 47th birthday today. This is also my first trip out of Australia and it is also my last,' said a woman waiting for the buses who asked not to be named.

France announced it has chartered an aircraft to help its stranded nationals get home. The flight will arrive on Tuesday and depart the following day, with priority given to 'the most urgent situations,' its Foreign Ministry said in a statement.

Thailand's government has alleged that the protesters are trying to spark anarchy so the military will feel compelled to take over the country.

But the army, which overthrew Thaksin and has a history of previous coups, says it has no plans to oust the current prime minister. Still, it has failed to back up Mr Somchai's efforts to restore order.

The supporters of the alliance are largely middle-class citizens who say Thailand's electoral system is susceptible to vote-buying and argue that the rural majority - the Thaksin camp's political base - is not sophisticated enough to cast ballots responsibly.

They have proposed discarding direct elections of lawmakers in favor of appointing most legislators, fostering resentment among rural voters.

The divisions have slipped into deadly violence. So far, six people have been killed in bomb attacks, clashes with police and street battles between government opponents and supporters. -- AP, REUTERS