"But there would be a lot of consequences including the international reaction."

"We will send him [the prime minister]a letter to inform that he must dissolve the house and call new elections."

Larry Jagan, a journalist and commentator based in Bangkok, told Al Jazeera that Somchai would probably be forced to take tougher action against the anti-government People's Alliance for Democracy (PAD), which accuses the government of being tainted by corruption and of being a puppet of Thaksin Shinawatra, the exiled ex-prime minister who was ousted from power in a 2006 coup.

"I think he is going to have to act and the possibility is that he will call a state of emergency, declare martial law, so that the authorities can deal more effectively with the protesters," he said, adding that the key issue was whether the military would step in.

"What we're seeing is a battle between the traditional elites who want to return to something like a paternal democracy and the new middle classes under Thaksin, the former prime minister, who really want to open up Thailand and see a global presence for the country."

Activist shot dead

The call came after a day of clashes between supporters of the ruling People's Power Party (PPP) and anti-government protesters left one man killed and many others wounded.

Key facts: The PAD


Group is a loose coalition of royalists, businessmen and urban middle class -Thailand's traditional elite.

PAD led protests that triggered 2006 coup against the then PM, Thaksin Shinawatra.

Supporters wear yellow shirts, a colour associated with Thailand's revered king.

Group accuses Thaksin supporters of pushing to turn Thailand into a republic, an allegation rejected by Thaksin.

Critics say PAD's contempt for results of three democratic elections show it is neither popular nor democratic.

Click here for more on the PAD

Police said a group of government supporters shot dead an anti-government activist as rival groups clashed in the northern city of Chiang Mai, shortly after the prime minister arrived in the city.

Suvarnabhumi airport was closed after PAD supporters stormed the main terminal.

Reports said three people were also injured on Wednesday after an explosive device, thought to have been a grenade, detonated at the airport.

With tensions on the rise, pro-government groups have said they will march through the streets of Bangkok in support of Somchai, setting the stage for fresh confrontations.

Thousands of travellers are stranded at the airport, Thailand's main international gateway and an important regional hub, following the clashes.

Incoming flights have been diverted to other airports around Thailand and the region, while the director of Suvarnabhumi airport said negotiations were underway with the protesters to allow stranded passengers to fly out.

'Damaged reputation'

"The incident has damaged Thailand's reputation and its economy beyond repair," Serirat Prasutanont said.

Protesters from the PAD, some armed with metal rods, stormed the airport on Tuesday night and appeared to be digging in for long siege in an effort to raise the stakes in the confrontation with the government.

The apparent ease with which the protesters took over what should normally be a tightly-guarded airport has raised questions over the degree of support in the Thai military for the protesters' cause.

Somchai and his cabinet set up temporary offices at the old airport after the grounds of Government House in central Bangkok were occupied by protesters in August.