One person died after a car bomb exploded near the protest area, officials said, and Ramathibhodi Hospital officials confirmed that a woman died from severe chest injuries suffered in the clash with police.

More than 420 people have been hurt, hospital officials said. A deputy prime minister who was charged with negotiating with the demonstrators resigned over the crackdown.

The protesters first prevented lawmakers from entering Parliament to hear newly sworn-in Prime Minister Somchai Wongsawat give his first speech to the legislative body.

After the sparsely attended session - some lawmakers were unable to get through the barricades and some opposition party members boycotted - the legislators were temporarily prevented from leaving by demonstrators who locked the exits. Authorities flew in three helicopters to pluck Somchai to safety.

Paramedics say they expect the injury toll to rise as demonstrators continued to clash with police.

The anti-government protesters are trying to lay siege to other government buildings near the Parliament in the capital city, Bangkok.