At least one Thai anti-government protester was killed and 21 were wounded in a pre-dawn bomb blast Thursday inside a demonstration site in Bangkok, emergency services said.

The bomb went off at 3:28 am (2028 GMT) in front of a stage at the Government House compound, which protesters from the so-called People`s Alliance for Democracy (PAD) occupied in late August.

Twenty-two demonstrators wounded by the bomb blast were taken to four nearby hospitals, emergency services said. One later died and 11 were still in a serious condition, they said.

`It`s a powerful bomb, so far one has died. We are still waiting for forensic officials and for PAD permission to go into Government House,` local police commander Colonel Somchai Chueyklin told AFP.

An emergency medical official speaking on condition of anonymity also confirmed that one man had died.

`Ten are in critical condition at (army-run) King Mongkut hospital, one serious at Ramathibodi hospital. The man died at Ramathibodi hospital` the official said.