Thousands of government supporters rallied in Bangkok yesterday, stoking fears of violent clashes with militants who have held the international airport since last week and brought the region's busiest hub to a standstill.

The protests came after several grenade attacks against the fiercely royalist anti-government People's Alliance for Democracy (PAD), which injured as many as 52 people and raised fears of open violence in Thailand's worst political crisis in decades.

In one attack a grenade was hurled into the Prime Minister's compound in central Bangkok, which has been held by the yellow-clad PAD since August. PAD militants have attacked police trying to order several thousand of them to leave Suvarnabhumi airport, chasing riot squad officers away from the terminal and letting air out of their vehicle tyres.

PAD guards, armed with staves and clubs, have blocked roads into Suvarnabhumi - Thailand's main airport - checking identification before allowing access. Egged on by speeches from its leaders, the group said that it would “fight to the death” before surrendering Suvarnabhumi. The Prime Minister, Somchai Wongsawat, the leader of the ruling People Power Party, has refused to step down as demanded by the PAD. He has instead moved the seat of government to the relative safety of the northern city of Chiang Mai, a stronghold of government support.

Panitan Wattanayagorn, a political scientist at Chulalongkorn University, said he believed the two sides were slowly moving from posturing and isolated acts of violence towards open confrontation. He said: “With everybody moving into tight corners, nobody knows what will happen.” Polls showed that 60 per cent of Thais did not support either side, he added.

With Bangkok's Suvarnabhumi and Don Muang airports at a standstill for more than five days, pressure is on the Government to find a solution, salvage Thailand's tourism industry and find a way to assist as many as 100,000 stranded tourists, including perhaps thousands of Britons, to return home.

Openly hinting that he fears a military coup, Mr Somchai is awaiting a Constitutional Court decision - perhaps as early as tomorrow - that may dissolve his party if it is found guilty of vote-buying charges. Dr Panitan said that the King's birthday speech scheduled for Thursday might also push either side into giving way.

Meanwhile, thousands of hot and weary tourists, desperate for a flight home, crowded into U-Tapao military airbase, 90 miles south of Bangkok, which has been pressed into service. It has a small terminal with one X-ray machine and two sets of wheeled air-steps. As tempers frayed and tourists began shouting and shoulder-charging the glass doors into the terminal, Anne Ryan and Andrew Carter, from London, waited for newly purchased seats on a flight out of Thailand.

Originally booked on Eva Air, they said they could not afford to wait indefinitely for a flight home. Eva Air had told them, they said, that December 11 was potentially the first date that they could fly, and that had to be confirmed. “We've got to get back,” Ms Ryan said. “There's life and work and animals waiting for us.”

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