BANGKOK, THAILAND - Eight Thai anti-government protesters were wounded, one critically, in a pre-dawn grenade attack in Bangkok Saturday, ramping up tensions a day ahead of a major rally, officials said.

The explosion came two days after one person was killed and 29 were wounded in a similar attack on demonstrators who have occupied the prime minister's offices in the capital since August.

The latest blast hit a checkpoint manned by guards from the anti-government People's Alliance for Democracy outside the Government House compound they are occupying, an emergency services spokeswoman said.

A man on a motorbike apparently threw a hand grenade into the protest camp, the PAD's website said. It confirmed that eight people were wounded and said the critically hurt man was aged 33.

Most of the wounded were "volunteer" guards at the site, it said. The PAD has set up strict security around the compound, where hundreds of protesters usually sleep, after a series of attacks.

The PAD had already called for a mass rally to blockade parliament on Sunday in response to Thursday's fatal grenade assault on protesters. It has blamed the government for the earlier attack and called on it to step down.

The movement alleges that the government is a corrupt proxy for former premier Thaksin Shinawatra, who was ousted in a bloodless military coup in 2006 after protests that were also led by the PAD.

After a brief lull in Thailand's political crisis because of a royal funeral last week, fears of violence at Sunday's rally are running high.

A similar protest on October 7 ended with fierce clashes between police and demonstrators that left two people dead and at least 500 wounded.

The crisis started after Thaksin's allies won elections in December, angering the old power cliques in the bureaucracy, military and palace who loathe the populist telecoms tycoon. --AFP