Up to 40,000 "Red Shirts", a movement tied to the ousted Thai prime minister Thaksin Shinawatra, marched on Government House late on Saturday night, breaking through police barriers to reach the gates of the compound before midnight.

"We demand that the Government returns power to the people because they do not have the mandate of the majority," said a protest leader, Jatuporn Phromphan. "We will continue to pressure them until they quit."

The scene was reminiscent of an earlier siege on Government House by the People's Alliance for Democracy, also known as the "Yellow Shirts", in late August. That resulted in the occupation of the seat of administration for three months and the eventual fall of the government.

The alliance was a staunchly anti-Thaksin movement, while the United Front for Democracy against Dictatorship "Red Shirts" are pro-Thaksin and oppose the newly appointed government of the Prime Minister, Abhisit Vejjajiva.

Unlike the alliance, the united front does not have the backing of Bangkok's political elite, which includes the military, so its protests have been more constrained than the alliance demonstrations, which culminated in the seizure and closure of Bangkok's two airports from November 26 to December 3.

The united front leaders issued four demands, including that the Government prosecute the alliance leaders for closing the airports and causing millions of dollars in losses to the economy.

"We want to know why none of their leaders have been arrested when they clearly broke the law by occupying airports," Mr Jatuporn said.

They also demanded that the Government dismiss the Foreign Minister, Kasit Piromya, who was an alliance leader, and revoke the 2007 constitution and dissolve the Government.

Mr Abhisit, who was attending the World Economic Forum in Davos this weekend, did not even mention the protest in his weekly television show yesterday, choosing instead to concentrate on the economic challenges facing the kingdom.

Mr Abhisit met several prime ministers at the forum in an attempt to win back investment confidence in Thailand, which has been undermined by three years of unprecedented political upheaval.

Thaksin was toppled by a military coup on September 19, 2006, ushering in a military-appointed government that was unpopular in Thailand and abroad.

Thaksin has been in self-exile since August, avoiding corruption charges, but continues to be a financier of the united front.

Deutsche Presse-Agentur