BANGKOK (AFP) - Thai anti-government protesters Monday ended a three-month sit in at the prime minister's offices, redeploying to help demonstrators tighten their paralysing grip on Bangkok's airports. Leaders of an alliance trying to force premier Somchai Wongsawat to resign said they were abandoning Government House because of recent grenade attacks which have killed two protesters and wounded dozens more. But in an apparent climbdown in the stand-off, which has left 350,000 travellers stranded, the People's Alliance for Democracy (PAD) allowed 37 empty aircraft to fly out of Suvarnabhumi international airport. "It's too risky to stay at Government House because of repeated attacks against us," PAD spokeswoman Anchalee Paireerak said. "All of us have started to move now." An AFP reporter saw hundreds of supporters carrying plastic bags and sleeping mats leaving the heavily fortified compound, last hit by a blast on Sunday that wounded 49 people. Another PAD spokesman, Suriyasai Katasila, said the movement hoped to hand over the site to the government on Tuesday morning. The royalist PAD seized the cabinet offices in August as part of a campaign they launched in May to topple an elected government they accuse of running the country on behalf of former premier Thaksin Shinawatra. Thaksin, who is Somchai's brother-in-law, was ousted in a 2006 coup. They took that campaign to unexpected heights last week, storming Suvarnabhumi on Tuesday and then occupying Don Mueang the next day as part of a "final battle" against the administration. Their departure from the premier's offices could ease the risk of clashes with protesters from a rival pro-government group who camped out in Bangkok for a second day just a few kilometres (miles) from Government House. The PAD are known as the "Yellow Shirts" due to the colour of their attire which symbolises devotion to Thailand's King " while the government's supporters are dubbed the "Red Shirts" because of their scarlet outfits. But fresh tensions were brewing after the Red Shirts threatened a blockade of Thailand's Constitutional Court, which is due Tuesday to wrap up a vote fraud case that could disband the ruling party and bar Somchai from politics. Police said they had asked the army to help protect the court. Meanwhile Somchai is due to attend a ceremony in Bangkok on Tuesday ahead of the birthday of the deeply revered King Bhumibol Adulyadej " but the premier is currently marooned in the northern city of Chiang Mai. Thais may also be waiting for the king, the world's longest reigning monarch, to point to a way out of the crisis in a birthday-eve speech on Thursday. Airport authorities however said Suvarnabhumi would remain shut for at least another two days, while a tourism ministry official put the number of stranded travellers at 350,000. The blockade claimed its first foreign victim, a Hong Kong man who died in a traffic accident while travelling to the southern town of Phuket where he was hoping to catch a flight home. Several nations stepped up emergency flights to evacuate frustrated holidaymakers. Australian airline Qantas and Air France-KLM sent extra planes to Phuket, while Spain and France dispatched aircraft to the Vietnam War-era U-Tapao naval base southeast of Bangkok, the main exodus point since last week. Exhausted passengers flocked to makeshift check-in desks set up at hotels in Bangkok on Monday. "I'll be happier when I see the runway," said Jason Payne, 33, from Sydney, Australia. Protesters say they will not disperse from the airports until Somchai steps down. Thaksin and his allies draw huge electoral support from Thailand's largely rural northern poor, while the PAD is backed by the Bangkok business elite and middle classes, along with elements in the military and the palace.