Thailand's main public sector unions are threatening to strike nationwide next week if the country's current administration does not step down.

The group of unions urged its nearly 200,000 workers to join an anti-government rally planned for Sunday in Bangkok.

Thailand's anti-government movement, the People's Alliance for Democracy, is organizing the mass rally after a grenade attack Thursday killed one protester and injured 23 others.

PAD leaders blame the government for the attack and say they will no longer tolerate what they say are the government's daily brutal crackdowns.  Prime Minister Somchai Wongsawat denies the accusations.

Thursday's attack occurred on the grounds of the prime minister's official compound, which has been occupied by protesters for nearly three months.

No one has claimed responsibility for the blast, and protesters have refused to allow police to enter the compound to investigate the blast.  

Protesters have been calling for the administration to step down since they began occupying Thailand's Government House compound in late August.

They say the current administration is too close to deposed Prime Minister Thaksin Shinawatra.  

The standoff has paralyzed the government and led to fears it will plunge Thailand into economic chaos.

Some information for this report was provided by AFP and Reuters.