The grenade-type explosion injured 22 other people supporting a campaign led by the People's Alliance for Democracy against the government, the Thai News Agency reported. Officials said the dead victim was a 48-year-old man.

Of those injured, four were reported to be seriously wounded.

TNA quoted witnesses as saying an explosive device was dropped into the Government House compound, which the protesters have occupied since Aug. 26. The PAD speculated the projectile might have been fired into the compounded from a military M-79 rifle, the report said.

Protesters have vowed to stay on at the compound until the current government resigns.

They claim the present government is corrupt and is only a proxy for former Prime Minister Thaksin Shinawatra, who was ousted in a 2006 military coup. Thaksin, who lives in England, faces several corruption charges, all of which he has denied.