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.
"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, for the time being, at least, the demonstrations have escalated 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. "The cabinet can still function, even though we are facing some difficulties. All sides have shown their political aims, now they must turn to face each other and talk in order to find a peaceful way out for the country."
As the protesters marched, they urged civil servants to join their campaign.
"We will protest peacefully, blowing whistles and handing out flowers," Suthep Thaugsuban, a former deputy prime minister under the previous Democrat-led government and now leader of the anti-government campaign, told a huge crowd on Sunday.
Thailand's National Security Council chief Paradorn Pattanathabutr said as many as 180,000 turned up to demonstrate on Sunday while police estimates put the crowd at 100,000.
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.
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Nevertheless, the former telecommunications tycoon, who fled just before his 2008 graft conviction, remains deeply mistrusted by the Bangkok-based establishment and many members of the middle class.
The protests have brought back memories of a tumultuous 2008 when anti-Thaksin "yellow shirt" protesters shut down Bangkok's airports and held crippling rallies against a Thaksin government, which was eventually disbanded by a court.
Yingluck's ruling Puea Thai Party received a blow last week when the Constitutional Court rejected its proposals to make the Senate fully elected. That could have strengthened her government given her widespread support among voters in the heavily populated north and northeast.
Supporters of Thaksin and Yingluck gathered in a stadium at the opposite end of the city, about 15 km (9 miles) away, say the court verdict is the latest attempt by anti-Thaksin forces to thwart the legislative process.
"The court has violated the rights of the people to change the charter. If our enemies try to stage a military coup, we will come out," Thida Thawornseth, leader of the pro-Thaksin United Front for Democracy Against Dictatorship, told Reuters.