BANGKOK - THAI anti-government protesters have blockaded and shut down a second Bangkok airport, an official said on Thursday, just over a day after they forced the closure of the main international airport.

Supporters of the so-called People's Alliance for Democracy (PAD) started massing at the main entrance to the old Don Mueang airport on Wednesday evening, and services there were cancelled at about midnight.

'Protesters have blocked the entrance to the terminal therefore we closed services until 6pm (5pm, Singapore time) on Thursday,' said Flying Officer Anirut Thanomkulbutra, director of Don Mueang.

Don Mueang operates a handful of domestic flights, and was the only airport left serving the capital after protesters swarmed the main Suvarnabhumi Airport late on Tuesday, forcing the airport director to suspend flights.

A police official said about 3,000 PAD supporters were gathered outside Don Mueang airport.

Protest leaders had said on Wednesday that they aimed to force the closure of Don Mueang to prevent ministers from flying to the northern city of Chiang Mai to meet with Prime Minister Somchai Wongsawat.

Mr Somchai returned from a summit in Peru, landing in Chiang Mai on Wednesday evening, soon after the powerful army chief urged the premier to call new elections to end six months of turmoil in the kingdom.

Mr Somchai refused, and called a cabinet meeting.

The premier had been holding cabinet meetings in a disused terminal at Don Mueang after protesters occupied his official Government House office in central Bangkok in late August.

But on Monday, PAD supporters besieged his temporary office as well as they upped their bid to topple the government, which they accuse of running the country on behalf of ousted and exiled premier Thaksin Shinawatra.

About 3,000 tourists were stranded at Suvarnabhumi as PAD supporters massed outside late on Tuesday, but they began leaving on Wednesday afternoon.

Protesters swiftly dug in inside the gleaming steel-and-glass terminal, setting up makeshift food stalls and tents in the airport.