A blast at Bangkok's international airport and grenade attacks elsewhere in the city wounded at least seven people on Wednesday, as lawlessness spread amid anti-government protests, officials said.

The explosion at Suvarnabhumi Airport happened a day after demonstrators stormed the airport, forcing it to close down and stranding thousands of passengers.

"At least two people were wounded by a bomb blast at Suvarnabhumi this morning," Petpong Kamchornkitkarn, an emergency medical services official, told AFP.

Two local television stations said a grenade was fired at protesters and that three people were wounded.