Bangkok  - Thousands of travellers were stranded at Bangkok's Suvarnabhumi International Airport Wednesday after their flights were cancelled by a siege on the facility by anti-government protestors.

Serirath Pasutanond, Airports of Thailand director in charge of Suvarnabhumi, estimated that 3,000 passengers had missed their flights after the airport was forced to stop departing flights Tuesday night.

Altogether, 73 flights, including 43 arriving aircraft and 30 departures, had been "impacted," Sirirath said.

Thousands of followers of the People's Alliance for Democracy (PAD) descended on Suvarnabhumi Tuesday evening in a bid to prevent the return of Thai Prime Minister Somchai Wongsawat from the Asia Pacific Economic Cooperation summit in Peru.

The protestors took control of the airport's entrances about 9 pm (1400 GMT) Tuesday, forcing the Airports of Thailand to announce the cancellation of departing flights for security purposes.

At least two bombs also went off in the parking lot of the airport early Wednesday, injuring four people, radio reports said.

The PAD - a loose alliance of disparate groups bound together by their hatred of Thaksin Shinawatra, a billionaire telecommunications tycoon who was prime minister from 2001 to 2006 - has been using increasingly violent tactics to overthrow the government.

Thai police and the politically powerful military have refrained from cracking down on the movement, which has support from a broad swath of Thai society, including members of Thailand's political elite.

Political observers said they saw no easy resolution to the confrontation between the PAD and the government, meaning the standoff was likely to be protracted.

"The country is at war, ... a war of legitimacy," said Panitan Wattanayagorn, a political scientist at Bangkok's Chulalongkorn University. "Both sides have a kind of legitimacy but not enough to get rid of the other."

Somchai leads an elected government, but the PAD claim he is a proxy for Thaksin, his brother-in-law.

Although living in self-imposed exile, Thaksin still controls the Thai government through his money, political cronies and relations.

Last month, Thailand's Supreme Court sentenced Thaksin to two years in jail for abuse of power for allowing his wife to successfully bid on a plot of land at a 2003 government auction.

PAD leader Sondhi Limthongkul called this week's protest the "final battle," vowing to bring the government down by Wednesday, after holding continuous street protests and demonstrations in Bangkok for six months.

The PAD on August 26 successfully seized and occupied Government House, the seat of the executive branch of the government. (dpa)