Protesters inside the Finance Ministry. They have called for the occupation of other government buildings. Damir Sagolj/Reuters

Protesters rest at the entrance of the Finance Ministry after occupying it. About 1,000 demonstrators forced their way into the building. Damir Sagolj/Reuters

Protest leader and former Deputy Prime Minister Suthep Thaugsuban, center, waves to protesters at the Finance Ministry. Damir Sagolj/Reuters

Anti-government protesters are blessed by supporting Thai monks in the grounds of the Thai Foreign Ministry, where they have set up a camp and occupied it. Barbara Walton/EPA

Anti-government protesters march toward Thailand's Finance Ministry in Bangkok on Monday, part of an effort to topple the government of Prime Minister Yingluck Shinawatra.

Thailand's Prime Minister Yingluck Shinawatra has invoked an emergency law after demonstrators seeking to remove her from office occupied parts of the Finance and Foreign ministries.

Yingluck announced on Monday that the Internal Security Act would cover all of Bangkok and the surrounding areas. Three especially sensitive districts of the capital have been under the law since August, when there were early signs of political unrest.

The law authorizes officials to seal off roads, take action against security threats, impose curfews and bar the use of electronic devices in designated areas. Peaceful rallies are allowed under the law.

Anti-government demonstrators occupied parts of the two ministry buildings, escalating protests that started over the weekend and drew over 150,000 people. They are calling for Yingluck to step down amid claims that her government is controlled by her brother, former Prime Minister Thaksin Shinawatra, who was ousted in a military coup in 2006.

The incursions into the ministry buildings were the boldest acts yet in opposition-led protests that started last month. They highlighted the movement's new strategy of paralyzing the government by forcing civil servants to stop working.

Protest leader Suthep Thaugsuban led the crowd at a rally at the Finance Ministry. Other protests snarled traffic across Bangkok.

"Go up to every floor, go into every room, but do not destroy anything," Suthep told the crowd before he entered the ministry and held a meeting in its conference room.

"Make them see this is people's power," said Suthep, a former deputy prime minister and an opposition lawmaker.

Protesters sang, danced and blew whistles in the hallways as part of the so-called whistle-blowing campaign against the government. One group cut power at the Budget Bureau to pressure the agency to stop funding government projects.

Police made no immediate move to oust them.

More than two dozen Bangkok schools along the protest route were closed Monday, and police tightened security at the protest destinations, which included the military and police headquarters and the five television stations controlled by the military or the government.