Bangkok - Unknown assailants launched a grenade at anti-government protestors Saturday, injuring eight people and fanning worries that Thailand was heading for more street violence this weekend, media reports said.

Witnesses said two young men fired the device from an M-79 grenade launcher at guards for the People's Alliance for Democracy (PAD) outside Government House, the seat of the Thai government, injuring eight people, one of whom was listed in critical condition with shrapnel wounds to his body and neck, The Nation newspaper's online news service said.

On Thursday, a similar early morning attack on the PAD left one man dead and 24 injured.

The attacks on the PAD, a loose coalition of groups adamantly opposed to the return to power of former premier Thaksin Shinawatra, have intensified in recent weeks.

The PAD seized Government House on August 26 and have occupied it since, demanding the resignation of the cabinet, which is now led by Prime Minister Somchai Wongsawat, Thaksin's brother-in-law, and packed with Thaksin nominees and political allies.

Thaksin, a former billionaire telecommunications tycoon who used his personal fortune and populist policies to dominate Thai politics during his premierships from 2001 to 2006, was toppled by a coup two years ago.

He has been living in self-imposed exile since August this year.

On October 21, the Supreme Court for Political Office Holders found Thaksin guilty of abuse of power for allowing his ex-wife, Pojaman, to successful bid on a prime plot of Bangkok land at a government auction in 2003. Thaksin was sentenced to two years in jail.

Thaksin criticized the verdict as being politically motivated and last week vowed to return to Thai politics despite his conviction.

The threat, along with recent attacks, has emboldened the PAD, which claims it would stage a mass rally of 100,000 people on Sunday to demand the resignation of the cabinet.

At its last mass protest on October 7, police opened fire on the PAD with tear-gas canisters, leading to a melee that left two PAD followers dead and hundreds injured.

More than 1,700 police have been assigned to keep the peace at Sunday's rally. (dpa)