One person has been killed and as many as 23 injured by an explosive device fired into an anti-government protesters' camp in Bangkok. The second explosives attack within weeks on the militants' camp in the grounds of the Prime Minister's residence has again ramped up fears that Thailand is teetering on the verge of outright civil conflict.

Within hours of the blast, leaders of the anti-government militants from the People's Alliance for Democracy declared they would not be intimidated by wanton violence. PAD militants have occupied the Government House compound since August, much to the chagrin of prime minister Somchai Wongsawat, who has been forced to relocate his offices to a disused airport.

PAD founder Sonthi Limthongkul alleged "murderous government sympathisers" had thrown an M79 grenade into the compound. "This morning's tragedy was not the first time the lives of the PAD supporters were threatened by a deadly bombing by government officials and money-for-hire killers of the traitorous government," he said. "There have been a series of brutal bomb attacks against the supporters of the PAD, who are mostly women, the elderly and children."

Mr Sonthi called for a mass rally this Sunday at the Government House compound to show PAD supporters remained undaunted by the violence. To demonstrate their confidence in their supporters, the PAD leaders have promised PAD will "go home", or end the Government House compound occupation, if fewer than usual militants show up.

The grenade landed on a tent roof and detonated at 3.25am, killing and wounding people who were peacefully asleep, Mr Sonthi said. At the compound, a flapping rip in a yellow tarpaulin roof bears mute testimony to the mayhem. Yet hundreds of PAD militants were today still in residence, sleeping, eating and listening to speeches. Kamrong Thongma, a retired bank official and PAD supporter, said he was woken by the blast. "I saw many people injured by the bomb," he told The Times Online. "They were screaming and there was a lot of blood. It was mainly women."

Yet, he said, he was not intimidated by the explosion, and he expected PAD supporters to rally to the cause and fill the compound grounds tonight. The current Thai government, he said was an "illegitimate, vote-buying mob that want to change the constitution so criminals go free.

"First we want the government out, and then we will get good politicians in office," he added.

Following the explosion, PAD guards immediately locked down the compound and refused entry to the police. The attack came just one day after the end of an informal ceasefire observed to respect the funeral of the king's sister, Princesss Galyani Vadhana, and it follows mounting speculation that the PAD movement is losing its popular support.

Suwan Kansanoh, a retired government official and ardent PAD militant, said the attack would not scare his compadres. Mr Suwan had left the compound just a couple of hours before the grenade exploded, but he said he would not be intimidated, and he averred he would return to the compound tonight. "We believe there will be more people in the compound tonight to show support," he said.. "After I have finished my work I will going back."

Pro-government forces – including serving members of the military - have recently upped their threats of violence in order to scare off the PAD invaders. Mr Suwan said it was ridiculous to expect any official protection or proper investigation of the attacks. The Thai police, he said, would be permitted into the compound later today, but he expected nothing to come of their visit. Nothing had been done about the last grenade attack, late last month, which injured ten PAD guards, two seriously. "We know there's nothing when they come," he said. "The last bomb, there's nothing moving forward, no investigation."

A PAD spokesman said the injured supporters had been sent to various hospitals in Bangkok. One of the injured was said to be in a coma.

When the PAD militants rallied outside Parliament House early last month, police fired exploding tear-gas bombs into the crowd, killing one PAD supporter and injuring hundreds. Today's attack will further intensify bitterness in the battle for Thailand's political future.

Times Recommends

• Would you live on the wrong side of the Berlin Wall?
• Wish you were here, says Iraq tourist board
• Russian policeman’s corruption plea to Putin