Bangkok airport was brought to a standstill by anti-government protesters today.
Flights at Suvarnabhumi International Airport were temporarily suspended shortly before hundreds of demonstrators - some masked and armed with metal bars - broke through police lines and spilled into the passenger terminal.
Airport manager Serirat Prasutanon said airport authorities had tried to negotiate with the protesters "but to no avail."
"For the safety for passengers, we have to stop flights out of the airport temporarily until the situation returns to normal," he said in a statement, adding that incoming flights were still operating.
He said the governor of Samut Prakan province, where the airport is located, had asked the army to help police.
Travelers seemed bewildered by the turn of events.
"This is the first time I have seen anything like this. I am glad that it did not turn out violent," said Daniel Garmona, a tourist from North Carolina who was waiting for a flight back to the US
Using trucks and cars, demonstrators cut off road access to the airport, the transportation hub for millions of tourists who visit the country each year.
The airport siege followed a clash earlier in the evening between opponents and supporters of Thailand's government.
Members of the anti-government People's Alliance for Democracy were returning from a rally at the smaller Don Muang airport, when government supporters threw rocks at their truck.
Alliance members responded by firing catapults and a half-dozen shots with two pistols from their truck.
The footage showed the alliance supporters surrounding a motorcycle taxi driver and putting a knife to his throat. After the driver fled, the protesters battered several motorbikes with steel bars and set fire to another one.
The clash was the second time in recent months that the two sides have fought and marks the first major violence since October 7, when street battles with police and anti-government forces left two people dead and hundreds wounded.
In a September clash between the two sides, a government supporter was beaten to death, while two alliance members were killed last week in grenade attacks.
Political tensions that have been simmering since 2006, when a similar protest campaign against then-Prime Minister Thaksin Shinawatra led to him being deposed by a military coup.
Tensions heated up further with the current effort to force Prime Minister Somchai Wongsawat to step down. The protesters accuse him of acting as a proxy for Thaksin, his brother-in-law.