BANGKOK, Thailand — Hundreds of pro-government demonstrators swarmed around a court building Tuesday, forcing the relocation of judges who will rule on the fate of a Thai government beset by protests and a virtual shutdown of international air links.

Judges of the Constitutional Court had to scurry to a suburban courtroom where they are to decide whether Prime Minister Somchai Wongsawat and others in his party committed electoral fraud _ a move that would see him banned from politics and his party dissolved.

The protesters followed the judges to the new location, shouting "Fight, fight," as dozens of soldiers carrying riot shields and batons and about 100 riot police guarded the court compound.

Hours earlier, an explosive device was hurled into a crowd of anti-government protesters at Bangkok's domestic airport, killing one person and wounding 22, said Surachet Sathitniramai of the Narenthorn Medical Center.

The court is expected to rule this week, and if the decision goes against Somchai it could dampen protests by the People's Alliance for Democracy, which has been seeking Somchai's ouster through daily protests and the seizure of Bangkok's domestic and international airports.

But it could also inflame pro-government supporters who have been gathering their strength in recent days and widen an already dangerous rift in Thai society, further paralyzing government machinery and draining the economy of millions of dollars.

Late Monday, the explosive device fired from an elevated highway fell among hundreds of protesters, some of them asleep, inside Don Muang domestic airport, Surachet said. A protest leader, Somsak Kosaisuk, said the crowd was hit by a grenade from an M-79 launcher, a battlefield weapon.

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It was the third such attack in two days by unidentified assailants targeting the protesters. So far, seven people have been killed and scores injured in bomb attacks, clashes with police and street battles between government opponents and supporters.

Neither the army, a key player in Thai politics, nor the country's much revered king have offered Somchai the firm backing he needs to resolve the crisis. Many Thais hope that the court ruling will help defuse it.

Even if Somchai is removed and the protesters disperse, it is expected to take at least another week before the airports become operational again.

The airport closure has severed all commercial flights in and out of the capital, forcing thousands to cancel their vacations during peak tourist season, and halted vital postal air services, preventing the arrival of everything from specialized medicines to fish for Bangkok's restaurants.

Authorities say more than 300,000 travelers are stranded in Thailand, with that number growing daily. The lucky ones are being flown out of a provincial airport with limited passenger capacity or are making their way overland to neighboring Malaysia.

Tourism, the country's top foreign currency earner, is not the only industry to take a big hit. Standard & Poor's has revised the credit rating outlook for Bangkok Bank, the country's biggest, from stable to negative. It issued similar downgrades for seven other major enterprises and for Thailand in general.

The credit rating service said in a statement Monday that the airport occupation "has caused serious disruptions to economic activities in the kingdom and raises the possibility of widespread violence markedly."

Somchai has been working out of Chiang Mai since last Wednesday, saying he wants to avoid confrontation with the protest alliance.

The protesters accuse Somchai of being a puppet of ousted Prime Minister Thaksin Shinawatra, the alliance's original target. Thaksin, who is Somchai's brother-in-law, was deposed in a 2006 military coup and has fled the country to escape corruption charges.

Alliance 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 political base _ is not sophisticated enough to cast ballots responsibly.

They have proposed discarding direct elections in favor of appointing most legislators, fostering resentment among rural voters.

The Constitutional Court was to hear closing arguments Tuesday in the electoral fraud case against Somchai's People's Power Party and two other parties in the governing coalition.

If found guilty, the parties would be dissolved and Somchai and 23 other lawmakers could be barred from politics for five years. Somchai's removal from office would bring down his government, but other members of his dissolved party would be free to join other parties and form a new government.

"This may diffuse the crisis but it won't end it. We will have to wait and see what the court says, but even if the parties are disbanded and the government is disqualified, they can regroup under a new umbrella and form a new government," said Panithan Wattanayagorn, a political scientist at Bangkok's Chulalongkorn University.

"However, the ruling would allow the protesters to say they have achieved their objective of getting rid of the government so it might solve the immediate crisis at the besieged airports," he said.

Protest leader Chamlong Srimuang said his group's "objective" would be achieved if the government falls.

But Veera Musikapong, a pro-government leader, said the court case against Somchai was part of "a coordinated effort to overthrow the government."

"It looks like justice is being done but it's nothing more than a hidden coup," he said.

"We have the right to question the court's ruling," said Sujit Wongmaingam, one of the protesters outside the court. "We already know what it will be and we won't accept it. They can't stage a real coup so they are using the courts to take power from the people."

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Associated Press reporters Ambika Ahuja, Jocelyn Gecker and Mick Elmore contributed to this report.