BANGKOK - Taxi drivers joined growing anti-government protests in Thailand on Thursday, blocking roads and causing gridlock across Bangkok, as supporters of ousted premier Thaksin Shinawatra threatened to disrupt an Asian summit.

Prime Minister Abhisit Vejjajiva was forced to return to the capital by helicopter after a meeting of economic ministers in Pattaya, the resort town that will also host the summit of Asian leaders starting on Friday.

The United Front for Democracy against Dictatorship (UDD), stepping up its action to force Abhisit to resign, said its supporters would travel to Pattaya and block access to the hotel where the summit will be held.

We apologize to partners of Thailand, but we need to show them that the Thai people do not accept this government, Jatuporn Prompan, a UDD leader, told a news conference.

Thaksin, toppled in a coup in 2006, lives in self-imposed exile, but his absence has not healed the divisions between the royalist, military and business elite, who say he was corrupt, and the poor who benefited from his populist policies.

His supporters say Abhisit, elected by parliament in December, is a pawn of the army and want new elections, which analysts say Thaksin's allies could win.

As many as 100,000 red-shirted Thaksin supporters had assembled on Wednesday in the area around Abhisit's office at Government House. On Thursday afternoon the numbers were put by witnesses at around 30,000 but other flashpoints were appearing.

Taxi drivers, a group that has supported Thaksin in the past, blocked major junctions in central Bangkok, traffic police said.

The Thai bourse is getting concerned. It ended flat on a day when many other Asian markets extended a recent tentative rally that has eluded Bangkok. An attempt to move higher faded after news of the traffic blockade spread.

Business leaders worry about the effects of political turmoil on the economy, already heading into recession after a slump in exports. Data on Thursday showed consumer confidence fell for a second month in March, with political uncertainty a factor.

PEACEFUL, SO FAR

The protests have been peaceful so far, and Abhisit said the gatherings could continue provided they stayed that way.

My standpoint remains the same: the rally can continue as long as they act within the framework of the law, he told Channel 9 television.

But the UDD has said it would step up its protests if Abhisit refused to quit by Thursday.

We've tried the soft approach. We've given them many chances already. Now we will show them what we are capable of, UDD leader Adisorn Piangkate told the crowd, wearing the red shirts adopted by Thaksin supporters, outside Government House.

Abhisit said the protests posed no security risk to the Asian summit to be held in Pattaya, 150 km (90 miles) south of Bangkok, brushing aside an incident on Tuesday when his car was attacked after he left a cabinet meeting at the same venue.

Foreign ministry spokesman Tharit Charungvat told Reuters in Pattaya that security was in place and contingencies drawn up.

We want to solve these problems without any confrontation. The prime minister has stressed the situation is under control and we have nothing to worry about, he said.

Finance ministers from the 10-country Association of South East Asian Nations (ASEAN) met in Pattaya on Thursday. A three-day summit of Asian leaders follows from Friday.

The summit had to be canceled late last year because of political unrest when a pro-Thaksin government was in power. Abhisit's administration has billed the rescheduled event as a sign Thailand was getting back to normal.

Abhisit has refused to use force to disperse the protesters. In that, he has learnt a lesson from history, said Economics Professor Lae Dilokvidhyarat from Chulalongkorn University.

History since the 1970s has showed that every civil strife or coup in this country was triggered or stemmed from the government, police or soldiers starting a crackdown, he said.

As long as this government can restrain itself in the face of provocations, and can control police and soldiers, I think we won't see riots or widespread street fighting.

Thailand