"While the government will enforce the laws it will not use force against the people," Prime Minister Yingluck said as she invoked the Internal Security Act in the entire capital and surrounding areas.
"The government would like to ask people not to join illegal protests and to respect the law," she said.
The move came after hundreds of anti-government protesters stormed into the finance ministry compound and later forced their way into the foreign ministry building.Both the compounds were apparently left unguarded.
The anti-government protesters broke down the gates to the foreign ministry and after occupying an area of the compound they asked civil servants to leave and not to return to work tomorrow, an official said.
"Tomorrow we will seize all ministries to show to the Thaksin system that they have no legitimacy to run the country," said Suthep Thaugsuban, a former opposition MP.
"It was a peaceful seizure by the people," Suthep told a press conference from the finance ministry.Anti-government protesters want Yingluck to step down amid claims that her government was remote-controlled by her older brother Thaksin Shinawatra, who was forced to quit as the Prime Minister in 2006.
He has since lived in exile to avoid jail on a corruption conviction except for a short visit to Thailand in 2008.The current political crisis is the most serious confrontation in Thailand since the 2010 bloody protests in which over 90 people were killed.
Earlier, protesters chanting "Thaksin get out, army come in", called for the intervention of the military in a country that has seen 18 actual or attempted coups since it became a constitutional monarchy in 1932.
Thailand's Opposition Democrat party leader and former premier Abhisit Vejjajiva today urged Yingluck and the ruling Pheu Thai Party to take responsibility for the protests. He said the large number of people gathering was a significant expression of the Thai society who want to see a change.