Police in Bangkok stood aside and removed barriers to let demonstrators reach Government House and police headquarters in an apparent truce after days of violence in which at least four people died amid demands for the government of Yingluck Shinawatra to resign.

Protest leaders had stressed they would not negotiate and promised to continue their efforts to oust Yingluck Shinawatra's administration. But with Tuesday came an unexpected twist as police took down barriers shielding their headquarters and let protesters in – seemingly to defuse demonstrators threats' to seize the building by force. Police also watched idly as crowds breached the barricades around Government House, the prime minister's offices.

It had earlier been speculated that some kind of an understanding was being brokered to allow the protests to pause for King Bhumibol Adulyadej's birthday on Thursday. The king, who turns 86, is highly revered by all Thais and is seen as the sole uniting figure in the country.

After breaching the barriers on the road, protesters milled outside the gates of the prime minister's office. Many took pictures of themselves. "This is a victory for the protesters," said Kusol Promualrat, wearing a military camouflage green jacket in front of the gate.

The man leading the demonstrations, Suthep Thaugsuban, 64, a former opposition lawmaker, had earlier issued Yingluck an ultimatum to "return power to the people" by Tuesday. He and his Civil Movement for Democracy (CMD) aim to overthrow the democratically elected government and install a so-called "people's council" manned by unelected representatives under the king as head of state. The CMD argues Yingluck's administration is a puppet of her brother Thaksin, the former PM who was ousted in a 2006 military coup and now lives in self-exile in Dubai and London.

A Thai Buddhist monk in a gas mask during earlier scenes as police used teargas and water cannon. Photograph: Dylan Martinez/Reuters

Yingluck on Monday vowed to do whatever it takes to "bring peace back to the Thai people" after the protests continued in the capital, where at least four people have been killed and 200 injured in a push to overthrow the government.

Seemingly contradicting an interview she gave to the BBC last week, in which she said she would neither step down nor hold early elections, Yingluck told a press conference that "the government is not trying to cling to power".

"I am not against either resignation or dissolution of parliament if this solution will stop the protests," she said.

"If there's anything I can do to bring peace back to the Thai people I am happy to do it. The government is more than willing to have talks but I myself cannot see a way out of this problem that is within the law and in the constitution."

Protesters had said they were unwilling to negotiate and would only back down once the "Thaksin regime" was fully overthrown. In a televised address on Monday night Suthep vowed to fight as long as need be, even alone, until Yingluck had been removed from office. "They can always come back to suck the blood of people, steal from people, disrespect the constitution and make us their slaves," he said in an apparent reference to the Shinawatra family.

The leader of the anti-government protests, Suthep Thaugsuban, during a rally at the government complex in Bangkok. Photograph: Narong Sangnak/EPA

While protests have taken place throughout the past week around Bangkok – primarily in relation to a proposed amnesty bill that would have paved the way for Thaksin's return from exile and squashed his corruption conviction – the violence only really ramped up on Saturday, when pro-Thaksin redshirts fought with anti-government student demonstrators near a sports stadium. At least four people have been killed and over 200 injured since.

On Monday much of the violence had centred around Government House, the seat of the prime minister's offices, and police headquarters.

Protesters threw rocks, bottles and homemade explosives at police in riot gear, who retaliated with water cannons and rubber bullets, and faced a standoff after protesters used rubbish trucks and bulldozers to try to overrun barriers.

Doctors at a Bangkok hospital confirmed on Monday that two patients had been treated for gunshot wounds from live rounds, although it was not clear who the gunmen were. Thai police insist they are only using rubber bullets, and Yingluck's government has taken great pains to use as little force against protestors as possible.

Although Suthep has claimed that the military is on his side, Yingluck told the nation that the military was acting neutrally and "wants to see a peaceful way out".

"I believe that no one wants to see a repeat of history, where we saw people suffer and lose their lives," she said.

The political violence has been Thailand's worst since the 2010 demonstrations that saw 2,000 injured and nearly 100 killed in a military crackdown.