Parliament postponed a joint session of both houses after protesters surrounded its gates and reportedly cut electricity to the building. House Speaker Chai Chidchob said the session would be rescheduled 'when the situation returns to normal'.

Despite fiery declarations that Monday's action would be their 'longest day,' a leader of the anti-government group - which calls itself the People's Alliance for Democracy - told followers to step up their protest efforts on Tuesday.

'Tomorrow is going to be more intense,' Chamlong Srimuang said to supporters at the group's stronghold at the prime minister's office, which it has occupied since late August. 'We request that you sleep well tonight to save your energy.'

Political tensions have been simmering since 2006, when a similar protest campaign against then-Prime Minister Thaksin Shinawatra led to him being deposed by a military coup. They heated up with the current effort to force Prime Minister Somchai Wongsawat to step down. The protesters accuse him of acting as a proxy for Thaksin, his brother-in-law.

The state planning agency said on Monday that Thailand's economy grew at its slowest pace in more than three years, taking a double hit in the third quarter from the political turmoil and the global financial crisis.

'Major services sectors such as manufacturing, hotels and restaurants, transport and communications, and wholesale and retail trade' showed slowed growth, said a report by the National Economic & Social Development Board.

Riot police early on Monday had barricaded Parliament with metal barriers and stood guard inside the compound.

Protest leaders say their goal is to block the government from functioning. The demonstrators called the protest to block Parliament from debating constitutional amendments that they say would help Thaksin stage a comeback.

'This is the final showdown,' protest leader Somsak Kosaisuk told the crowd, adding that 'they have robbed the country to the point where we can't take it anymore. I promise you this will soon end'.

Music blared through loudspeakers as protesters sang and danced on the streets outside, many with swimming goggles protectively on their foreheads in case police moved in with tear gas.

Both sides had feared violence would erupt. Protesters were flanked by their own guards armed with poles, clubs and metal rods.

The last time the group marched on Parliament, police efforts to disperse them with tear gas resulted in running street battles. Two people were killed and hundreds injured in the Oct 7 violence.

On Monday, riot police carrying with shields and batons yielded whenever protesters pushed hard.

By midday, most protesters returned to the prime minister's compound, while several hundred protesters moved to the government's makeshift office at Bangkok's former international airport but arrived there too late to interrupt a Cabinet meeting.

'One mission has been accomplished. We have won our victory here,' protest leader Mr Somsak said outside Parliament. 'We'll keep doing this until they quit.' During the days, militant protesters forced dozens of riot police to retreat into Bangkok's police headquarters, and another rally was staged at the Finance Ministry.

By evening, the numbers of protesters increased to several thousand at the airport, where a group of them attacked a senior police officer, throwing bottles at him, pushing him until he fell, and kicking him while he was down. He was rescued by fellow officers.

The alliance has accused police of being behind an attack last week in which grenades killed two protesters near the prime minister's office. Authorities have denied the charge.

Thaksin, who was ousted by a 2006 military coup, fled overseas in August to escape a slew of corruption charges. He has been sentenced to two years in jail for violating a conflict of interest law.

Thaksin, who is currently in Dubai, said he would return home if the king granted him a pardon.

'With me at the helm I can bring confidence quickly back to Thailand,' Thaksin told Arabian Business magazine. 'If they don't need me and the king feels I can make no difference, then I will stay here and do business.'

Mr Somchai was in Peru for a summit of Pacific Rim leaders and was expected to return at midweek.

The alliance's supporters are largely middle-class citizens who say Thailand's electoral system is susceptible to vote-buying and argue that the rural majority - the Thaksin camp's power base - is not sophisticated enough to cast ballots responsibly.

They propose replacing the elected Parliament with one that is mostly appointed, a move critics charge is meant to keep power in the hands of the educated, urban elite. -- AP

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