A sea of red shirts flooded Bangkok yesterday (March 13) in what organisers said was a 'final' push to force the Prime Minister to dissolve Parliament and hold fresh elections.

The movement's leaders gave PM Abhisit Vejjajiva a four-day deadline. Failing that, they threatened to spread their protests to 'all corners' of Bangkok.

By last night, the number at the rally of the United Front for Democracy against Dictatorship (UDD), notable for the red T-shirts its supporters wear, had reached about 45,000, police said. But hundreds more were arriving in the Thai capital every hour. The 'red shirts', as they are known for short, began trundling into Bangkok yesterday morning, in convoys of thousands of trucks, vans and buses.

Unarmed soldiers kept close watch but politely waved them through.

Yesterday evening, the National Security Council estimated that by this morning, the number of protesters would reach 100,000. But the numbers still arriving in the capital late yesterday indicated that the rally could surpass previous estimates of 150,000. UDD organisers said they still hoped to muster a million people, but realistically said they may reach half a million.

That, they said, would be a critical mass that Bangkok's establishment could not afford to ignore.

Jatuporn Promphan, a key red shirt leader, said that if the government held its ground, protests would intensify.

Another prominent UDD leader, Nattawut Saikuar, insisted that the red shirts' fight was not just about former prime minister Thaksin Shinawatra.

Last month's court verdict was beside the point, he said.

The ruling stripped Thaksin of some US$46 billion of his wealth on grounds that it had been acquired by rigging policy to favour his family-owned companies while he was premier from 2001 to 2006 before being ousted by the army.

But Thaksin, who is overseas dodging both a two-year jail sentence for corruption at home and the Thai government's attempts to extradite him, remained an important symbol for the movement.

Separately, the Thai government said that Thaksin had been asked to leave Dubai, his home in exile, by the government of the United Arab Emirates - at Bangkok's request - because he had used the country to destabilise Thailand.

The claim could not be verified, but when Thaksin called last night to speak to the rally, he said he was in Europe.

The crowd swelled by the hour below the ramparts of the late 18th century Mahakan Fort on the capital's Rajadamnoen avenue.

Soldiers with riot shields kept watch on the periphery.

But the rally remained peaceful and even festive. At one point, hundreds of pots of red chrysanthemums arrived to decorate the surroundings.

"We can sustain this rally for seven days," red shirt co-leader Kokaew Pikulthong said on the sidelines. Asked what the UDD would do if the government stood its ground, he said: "We have to pressure them harder."

Plans include a march around Bangkok tomorrow (March 15), in an attempt to paralyse the city and pile pressure on the government.

Yesterday, though, PM Abhisit said the situation was normal and appealed for calm.

Abhisit came to power some 15 months ago in a parliamentary vote and has so far refused to call an early election to prove that he has the backing of the majority of the people.

Thaksin, who became increasingly loathed by Thailand's traditional old elites, was elected three times. Most red shirts support Thaksin, saying he was the first prime minister to deliver real benefits to them, and see him as a 'victim' of the entrenched elites who could not tolerate his economic and political domination.