Protesters in Thailand's capital, Bangkok, cut off electricity to the prime minister's office compound and demanded that police abandon the premises.
Earlier on Thursday a group of student protesters cut through barbed wire and scaled the wall of Government House, where the prime minister's office is located.
The opposition-backed protesters, seeking to force the replacement of caretaker Prime Minister Yingluck Shinawatra's government before a February 2 election, have threatened to force their way in if police do not leave.
They want the building to be surrendered to the control of the armed forces.
Al Jazeera's Harry Fawcett, reporting from Bangkok, said opposition leader Suthep Thaugsuban has called on the military to take a stand and support the people.
"He wants a meeting with them some time today," he said. "The military is still considering whether they will heed this call, it would be a key development if the military does take a side."
Reuters reported that the armed forces chief said he would not meet the protest leaders.
The prime minister was not in her offices at the time and shortly afterwards gave a televised address from an unidentified location in which she announced a December 15 meeting of all sectors of society to try to find a solution to the crisis.
In a previous confrontation, police withdrew from the compound to allow the demonstrators in without a fight.
That withdrawal came after two days of increasingly violent stand-offs.