About 1,000 anti-government demonstrators forced their way into Thailand's Finance Ministry on Monday and protest leaders called for the occupation of other government buildings in an escalating bid to topple Prime Minister Yingluck Shinawatra.
The swiftly rising political tension came as more than 30,000 demonstrators marched to 13 areas across the city, raising the risk of a clash with police, a day after about 100,000 gathered in the city's historic quarter.
The protesters, led by the opposition Democrat Party, say Yingluck has become a puppet for her brother, former Prime Minister Thaksin Shinawatra, who was ousted in a 2006 military coup and convicted of graft two years later -- charges that he says were politically motivated.
Yingluck swept to power in a 2011 election that was seen as a victory for the working poor and a defeat for the traditional Bangkok elite that backs the opposition Democrats -- from top generals to royal advisers, middle-class bureaucrats and business leaders.
Many of Bangkok's working class have recently joined the protests, the biggest demonstrations since deadly political unrest in April-May 2010, when Thaksin's supporters paralyzed Bangkok to try to bring down a Democrat-led government.
"I invite protesters to stay here overnight at the Finance Ministry," protest leader Suthep Thaugsuban told a crowd gathered in front of the ministry. "I urge other protesters to do the same and seize other government buildings and offices around the country."
The protesters began the day chanting "Get Out!" against the government as they fanned out to state offices, military and naval bases and state television channels. A German photojournalist was attacked after a speaker at one protest site identified him as a pro-government sympathizer.
Nick Nostitz said he was punched several times before escaping behind nearby police lines.
The Finance Ministry's power was cut briefly after the protesters burst inside, a Reuters witness said.
The mounting tension condemned the baht currency to an 11-week low, down 0.4 percent to 31.97 to the dollar.
Anti-government rallies, which began last month, were triggered by a government-backed amnesty bill that could have led to the return of Yingluck's brother, ousted former premier Thaksin Shinawatra, without facing jail time for a 2008 corruption sentence.
Although the bill has been dropped, the demonstrations have grown into an all-out call for government change and the ouster of Yingluck who is widely viewed as Thaksin's proxy as he wields influence over government policies from a base in Dubai.
"This week is precarious. The options are very limited for the government," said Thitinan Pongsudhirak, a political analyst at Bangkok's Chulalongkorn University.
Yingluck, who faces a no-confidence debate on Tuesday, said she would not leave office.
"I have no intention to resign or dissolve the House," she told reporters.
As the protesters marched, they urged civil servants to join their campaign.
Suthep, a former deputy prime minister under the previous Democrat-led government, exhorted the crowd to seize the government's Public Relations department, a few blocks away from the Finance Ministry
By afternoon, about 500 protesters were inside the grounds but not inside the building, which is controlled by the office of the Prime Minister and home to government radio stations, according to witnesses.
Thaksin, who won elections in 2001 and 2005 by landslides, remains a populist hero among the poor, whose votes helped Yingluck and her party sweep polls in 2011.
But corruption scandals steadily eroded his popularity among Bangkok's middle class. That was compounded by royalist accusations that Thaksin was undermining the monarchy, which he denied.