The Constitution Court moved with unusual speed on Tuesday to dismiss Prime Minister Somchai Wongsawat and outlaw the ruling People Power party. Anti-government protesters lifted their Suvarnabhumi siege, but full international service could take two weeks to resume at the Bangkok airport.

PPP leaders vowed to form another government under the Puea Thai party label. But it will be without Mr Somchai, who was banned from politics for five years.

"My duty is over. I am now an ordinary citizen," Somchai, 61, told reporters in the northern city of Chiang Mai from where he has been governing since the blockade began.

Also banned by the court was the venerable Chart Thai party and the Matchimatipataya, both key members of the coalition government.

"As the court decided to dissolve the People Power Party (PPP), therefore the leader of the party and party executives must be banned from politics for five years," said Chat Chonlaworn, head of the nine-judge court panel, in the ruling on PPP.

"The court had no other option," he said.

It is expected that the three banned parties will reunite under the Puea Thai (For Thais) party, and form a government from surviving members of parliament.

Chaovarat Charnveerakul, the first deputy prime minister, will be caretaker prime minister.

Government chief whip Withaya Buranasiri said a proposal may be made for the House of Representatives to convene a session on Dec 8 to elect a new prime minister.

The court decision banned the parties and all their executives because of cheating in the Dec 23, 2007, election. But the decision has no immediate effect on other MPs or their ability to form a government.

At Suvarnabhumi airport, blockaded one week ago, there were scenes of jubilation by the yellow-clad People's Alliance for Democracy (PAD), whose goal was to topple the government.

PAD spokesmen said the protesters will "allow flights" to and from Suvarnabhumi, but warned they will stay at the factility and could retake control at any time.

"The next government must sincerely agree to introduce new politics and must not be a puppet regime for Thaksin Shinawatra," said a statement by the PAD.

The protest will continue in an area of the airport which will not interfere with passengers for now, said the PAD.

Later, PAD founder and core leader Sondhi Limthongkul announced the PAD will leave the airport on Wednesday and end all protests at 10am. Other leaders did not confirm his statement.

But, "As of this moment the PAD has allowed flights to take off and land immediately, both passenger and cargo flights," senior PAD member Somkiat Pongpaiboon told reporters at the airport.

All equipment at the airport would have to be checked over before full airport operations could resume, he said.

Serirat Prasutanont, chief of the Suvarnabhumi airport and acting director of Airports of Thailand (AoT), said the AoT needed to clean up and inspect security and damage at Suvarnabhumi and the main international airport would remain closed until Dec 15.

A statement said the closure of the airport for passenger flights "is extended to 6pm on Dec 15."

The statement by acting AoT director Serirat Prasutanont said the country's main airport has lost more $10 million from the week-long closure forced by the PAD protesters.

At the Stock Exchange, shares dropped after the verdict, as investors fear even more political chaos. The SET Index lost 3.60, or 0.9 percent, to close at 387.32, its lowest since Nov. 24.

The government officially cancelled the Asean summit planned for next week. The foreign ministry said it might be held in Thailand in March.

"The court had no other option," he said.

The verdict came amid a confrontation between Somchai, the brother-in-law of ousted former premier Thaksin Shinawatra, and anti-government protesters occupying Suvarnabhumi and Don Mueang airports.

Somchai was elected by parliament on September 17 after his predecessor, Samak Sundaravej, was forced from office last month for appearing in television cooking shows.

The judge, wearing a black robe with a scarlet collar, read the order live on national television.

"No matter whether you are satisfied or not with the verdict, we ask you to accept it," he said.

The verdict said the party must be disbanded because PPP executives had been convicted of vote fraud after elections in December 2007.

"Although some party executives had no knowledge of the election fraud, the law stipulates clearly... the party must scrutinise its executives thus the party cannot deny responsibility," Chat said.

The court banned 109 PPP, Chart Thai and Matchimathipataya executives from politics for five years. โ€” (AFP)