At least four rounds of bomb attacks rocked Bangkok early Wednesday, injuring at least 12 people, local media reported.

Anti-government protesters gesture as they blocked the main road to Bangkok's Suvarnabhumi international airport November 25, 2008. Flight operations at Thailand's main international airport were disrupted on Tuesday night after hundreds of anti-government protesters stormed the terminal building.[Xinhua/Reuters Photo]

The attacks, since 4:30 a.m. (2130 GMT Tuesday) to 6:30 a.m. ( 2330 GMT Tuesday) Wednesday, aimed at two main airports of Bangkok while three exploded at the Suvarnabhumi International Airport and one blast at the Don Muang Airport.

Both the airports were filled with the anti-government People's Alliance for Democracy (PAD) members who launched mass protests there since Tuesday.

Initial reports said at least 11 persons were injured.

According to local TV reports, three explosions were heard outside the outbound passenger terminal of the Suvarnabhumi International Airport at 4:30 a.m. (2130 GMT Tuesday).

The explosion sounds frightened the protestors as police vehicles rushed to the scene. The protestors feared that police would come to violently disperse them. But their leaders managed to calm them down minutes later.

The Suvarnabhumi International Airport, Thailand's largest air hub, was closed since Tuesday night since the mass protest has posed security threat.

Meanwhile, the explosion at the Don Muang Airport, where protestors were rallying, happened at 6:30 a.m. (2330 GMT Tuesday).

TV Channel 3 also reported that a grenade was also launched at the protestors but it did not explode.

On Monday, the PAD, which has seized the Government House since August 26, held mass protest before the Parliament, the Chart Thai Party Headquarters, the Finance Ministry and later changed their target to the temporary seat of government at Don Mueang Airport.

On Tuesday night, the Suvarnabhumi International Airport was sealed by the Airport of Thailand Authorities. Until Wednesday morning, hundreds of foreign flights have been canceled their Bangkok travel and more than 6,000 foreign passengers here had to wait for further information.

The PAD has vowed to topple the government by Wednesday.