
Witnesses said two young men had fired the explosive device from an M-79 grenade-launcher at guards of the People's Alliance for Democracy (PAD) outside Government House, which the group has occupied for almost three months.
One of the eight victims, identified as 22-year-old Anupong Samerphak, was pronounced brain-dead in hospital, having sustained shrapnel wounds to his body and neck, said Ramathipbodi Hospital director Dr Than Suphatphan.
PAD leader Chamlong Srimuang said the attack was the handiwork of a professional. "It had to be a soldier," he said at a press conference.
Another PAD leader, Sondhi Limthongkul, warned that the attack might spark a violent backlash.
"The government needs to take responsibility, because this kind of action will encourage people to take up weapons and fight the government," Sondhi said. "This will destroy the whole country."
On Thursday a similar early-morning attack on the PAD killed one man and injured 24 people.