Thailand's main international airport canceled all flights Wednesday as protesters thronged the complex and stormed the control tower in efforts to bring down the government, stranding thousands of tourists and buffeting the country's already-fragile tourism industry.

The demonstrators are now in the control tower, and say airlines must seek their permission to land. The protest group said it would remain at the airport despite a plea from the country's army commander to leave.

Gen. Anupong Paochinda on Wednesday afternoon suggested the protesters of the People's Alliance for Democracy withdraw and that the government call new elections to end the country's bitter political crisis.

Protest leader Suriyasai Katasila said the group would maintain its occupation until it could discuss the matter.

Meanwhile, Thai media says the prime minister has landed at a military airport in northern Thailand. He was out of the country, attending a summit in Peru.

The airport takeover was one of the boldest gambles yet by the People's Alliance for Democracy in its four-month campaign to topple Prime Minister Somchai Wongsawat, whom it accuses of being the puppet of a disgraced fugitive predecessor, billionaire Thaksin Shinawatra.

Exhausted travelers tried to sleep on suitcases, on luggage carts, on security conveyer belts, behind vacated check-in counters. Protesters dressed in yellow shirts walked around distributing food, ham sandwiches and packets of rice.

"We'd rather they just go home so we can go home," said Kay Spitler, 58, from Glendale, Arizona.

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Cheryl Turner, 63, of Scottsdale, Arizona, needed to get home to cook a feast for her family Thursday for the U.S. holiday of Thanksgiving. She said she had instructed her neighbors to pull a turkey from her freezer a day ahead of time.

"My turkey is sitting in the sink at home," she said.

The alliance vowed to bring its campaign to a final showdown this week, and violence has spiked, including streets clashes between supporters and opponents of the government Tuesday that included the first open use of firearms by the anti-government protesters. Police said 11 government supporters were injured, some with gunshot wounds.

Early Wednesday, assailants threw four explosives at anti-government protesters, including one targeting a group about a half-mile (1 kilometer) from Bangkok's main international Suvarnabhumi Airport.

A second was tossed into a crowd of supporters gathered at the domestic Don Muang airport, injuring three others, police said. Two other explosives were thrown in Bangkok but no one was injured.

Demonstrators — some masked and armed with metal rods — swarmed the international airport overnight, breaking through police lines and spilling into the passenger terminal.

The airport was fully shut down early Wednesday, resulting in 292 flights being canceled between 10 p.m. Tuesday and 6 p.m. Wednesday, with thousands of travelers stranded in airports in Thailand and elsewhere around the world.

Eighteen flights were diverted to Bangkok's Don Muang airport, which normally handles domestic traffic and a dozen others were rerouted to U Taphao military airport about 190 kilometers (118 miles) east of Bangkok, as well as to Hong Kong and Singapore airports, airport officials said.

Airport director Serirat Prasutanont said authorities were trying to negotiate with the protesters to allow stranded passengers to fly out.

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

The alliance said protesters would keep the airport closed until they get the resignation of Somchai, who was scheduled to return late Wednesday from an Asia-Pacific summit in Peru and was to land at a military airport.

The protesters appeared intent on forcing the military to intervene and bring down the elected regime. Army commander Gen. Anupong Paochinda has repeatedly ruled out a coup, though he has also said the army "will keep peace and order to protect the public and uphold important institutions like the monarchy."

The alliance has staged a number of dramatic actions in recent months. It took over the prime minister's office in late August and twice blockaded Parliament — one time setting off street battles with police that ended with two people dead and hundreds injured.

Support for the alliance has been waning in recent weeks, and the group appeared to be edging toward bigger confrontations — involving fewer though more aggressive followers — in hopes of creating chaos.

"Now, they are openly creating instability and provoking a military coup," said Thitinan Pongsidhirak, a political scientist at Bangkok's Chulalongkorn University.

The airport blockade is a fresh blow to Thailand's $16 billion a year tourism industry, already suffering from months of political unrest and the global financial crisis. Suvarnabhumi is the world's 18th largest airport in passenger traffic, handling over 40 million passengers in 2007.

An Australian couple was stranded at the airport since late Tuesday following two weeks on a beach on the resort island of Phuket for their honeymoon.

"Our main concern is to get the first flight home and never come back," said newlywed Robert Grieve, 32, of Melbourne, drinking a can of Heineken as he leaned against a vacated Thai Airways check-in counter. "I haven't even seen any staff since last night."

The anti-government protesters are mostly better educated, more affluent, urban Thais demanding that the country move away from a Western-style electoral system, which they say Thaksin exploited to buy votes. They instead favor a system in which some representatives are chosen by certain professions and social groups.

They are vastly outnumbered by Thaksin's supporters in the rural majority, who delivered his party two resounding election victories. Their loyalty was sealed by generous social and economic welfare programs for previously neglected provincial areas.

The anti-government forces are well organized, and have the behind-the-scenes support of elements of the military and parties close the royal palace, the country's most influential institution.