Samak flew to the nearby town of Hua Hin on Saturday, to meet King Bhumibol Adulyadej, Thailand's monarch, and brief him on the political situation as the occupation of the grounds of Government House by protestors moved into its fifth day.

The trip to Hua Hin  is his second meeting with the monarch in as many days.

The demonstrators have also invoked the king, both in speeches and with royalist imagery, but he has remained silent on the current standoff.

Continuing protests

Protesters have warned they will remain camped in the prime minister's official compound until Samak's government falls.

Behind their makeshift barricades, thousands of People's Alliance for Democracy (PAD) supporters milled around the Government House compound on Saturday, listening to speeches and singing patriotic anthems.

Sondhi Limtongkul, a PAD leader, said the demonstrations would not be halted until Samak, who is accused of being an illegitimate proxy of ousted prime minister Thaksin Shinawatra, was out of office.

"PAD members have agreed not to give up. Since they [Samak's party] took power in the election, they are trying to manipulate politics and interfere in the justice system," Sondhi said.

Clashes erupted briefly on Friday evening when a 2,000-strong crowd attacked Bangkok's police headquarters and about 30 people were injured as police repelled them with rubber bullets and teargas.

Since Tuesday Samak has worked out of defence complexes, including the country's military headquarters and the defence ministry.

The PAD expanded their campaign across the country on Friday, forcing the closure of three regional airports, provoking railway strikes and clashing with riot police in Bangkok.

About one quarter of Thailand's rail services came to a halt when nearly 250 drivers and mechanics called in sick to support the protests.

Call for emergency

Some of Samak's advisers have urged him to impose emergency rule, two government sources said.

A state of emergency would allow the government to deploy soldiers to disperse the protesters. But Anupong Paochinda, Thailand's army chief, has said the situation does not currently warrant it.

Police appeared to exercise restraint when the protesters, some armed with golf clubs, batons and bamboo sticks, forced 400 personnel out of the government house grounds early on Friday morning.

Samak and police officials have repeatedly said that force will not be used to remove the thousands of protesters.

Nine PAD leaders have been charged with insurrection, a crime that can carry the death penalty, after violent raids on government offices and a state TV station on Monday.