Thai protesters have marched on several government buildings on the second day of what they are calling a shutdown of the capital, Bangkok.
Demonstrators surrounded the Customs Department and key road junctions remained blocked.
The protesters want the government of Prime Minister Yingluck Shinawatra to be replaced by an unelected "people's council".
They say they will remain on the streets until their demands are met.
The protesters allege that Ms Yingluck's government is controlled by her brother, ousted former PM Thaksin Shinawatra, and say money politics have created a flawed democracy in Thailand.
Ms Yingluck - who leads an elected government which enjoys strong support in rural areas - has called a snap election on 2 February in response to the protests. The opposition is boycotting the polls.
On Monday, protest leader Suthep Thaugsuban appeared to rule out negotiations.
"You cannot mediate with this undertaking, you cannot compromise with this undertaking,'' he said. "In this undertaking, there's only win or lose... today, we must cleanse Thailand.''
Ms Yingluck reiterated on Tuesday that she was "asking for co-operation" from all sides.
"I am not holding onto my role as a caretaker, but am holding on to the rule of democracy which is owned by the people," she said.
On Monday thousands of demonstrators gathered in Bangkok to build barricades at seven major intersections.
Many slept outside overnight and on Tuesday groups headed to government buildings to try and disrupt officials' work.
The Customs Department was targeted early in the day by several thousand protesters.
"We have closed the entire department, but not customs checkpoints. We will see how the situation develops," customs director Rakop Srisupaat told AFP news agency.
The Commerce Ministry was also targeted, the Bangkok Post reported.
The shutdown has been peaceful so far and shops and businesses have remained open in unaffected areas.
The government, which says it wants to avoid confrontation, has deployed some 18,000 security personnel to maintain order.
Late on Monday, the US called on all sides to exercise restraint.
US diplomats were working with a "full range" of players "to encourage dialogue and a peaceful democratic political resolution", State Department spokeswoman Marie Harf said.