BANGKOK » Thailand’s prime minister invoked an emergency law today after demonstrators seeking to remove her from office occupied parts of the finance and foreign ministries.

Prime Minister Yingluck Shinawatra announced that the Internal Security Act would cover all of Bangkok and large parts of 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 ban the use of electronic devices in designated areas. Peaceful rallies are allowed under the law.

Protesters swarmed into the two government ministries earlier Monday (Sunday in Hawaii), overrunning several buildings and cutting electricity in an escalating campaign to topple Yingluck’s government.

Protesters say they want 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 for alleged corruption. On Sunday, more than 150,000 demonstrators took to Bangkok’s streets in the largest rally Thailand has seen in years, uniting against what they call the "Thaksin regime."

The incursions into the finance and foreign ministries 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.

The opposition Democrat Party, which is spearheading the protests and has lost to Thaksin-backed parties in every election since 2001, also plans to challenge the government Tuesday with a parliamentary no-confidence debate.

"The protesters have escalated their rally, which previously was a peaceful one," Yingluck said in a televised address. She said the government respected the people’s right to freely express opinions, but also had the responsibility to safeguard the country’s peace and stability and assets, along with the safety of citizens and their right to access government offices.

The law will cover the city’s international airports. In 2008, anti-Thaksin demonstrators occupied Bangkok’s two airports for a week after taking over the prime minister’s office for three months.

Protest leader Suthep Thaugsuban led the crowd at the Finance Ministry on a day when protesters fanned out to 13 locations across Bangkok, snarling traffic and raising concerns of violence in the country’s ongoing political crisis, which has revolved around Thaksin for years.

"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 opposition lawmaker.

Protesters sang, danced and blew noisy whistles in the hallways as part of their "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.

The protesters in the evening burst onto the Foreign Ministry grounds, which was not on their original list of targets.

"The protesters are on the ministry’s compound but they promised they will not enter the buildings," Foreign Ministry spokesman Sek Wannamethee said by phone. "We are now asking them to provide ways for the officials who were still working to leave the offices and they will likely have to work from home tomorrow." He did not know how many protesters there were, though Thai media said there were several hundred.

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.

Despite a heavy police presence at most protest sites, there was limited security at the finance and foreign ministries.

At another protest near the prime minister’s office, police were outnumbered by more than 1,000 protesters who scuffled with officers and tore down a razor wire barricade. A foreign freelance journalist in the crowd was punched by protesters who accused him of biased reporting before security personnel intervened.

Many fear that clashes could erupt between the anti-government protesters and Thaksin’s supporters, who are staging their own rally at a Bangkok stadium and have vowed to stay until the opposition calls off its demonstrations.

Thaksin’s supporters and opponents have battled for power since he was toppled in 2006 following street protests accusing him of corruption and disrespect for the country’s constitutional monarch, King Bhumibol Adulyadej. Thaksin has lived in self-imposed exile for the past five years to avoid a prison sentence on a corruption conviction.

The battle for power has sometimes led to bloodshed on Bangkok’s streets. About 90 people were killed in 2010 when Thaksin’s "Red Shirt" supporters occupied parts of central Bangkok for weeks before the government, led then by the current opposition, sent the military to crack down.

The latest protests have ended two years of relative calm under Yingluck’s government.

Yingluck’s administration has struggled to contain the demonstrations, which started over opposition to a government-backed political amnesty bill that critics said was designed to bring Thaksin home from exile. The Senate rejected the bill earlier this month in a bid to end the protests. But the rallies have gained momentum and leaders have now shifted their target to toppling the "Thaksin regime."