Police who had used tear gas, water cannons and rubber bullets to repel thousands of protesters removed barbed wire and barricades outside the buildings and declared they would no longer stand in the way of the protesters.

“The Metropolitan Police Headquarters belongs to the public,” said police chief  Kamronvit Thoopkrachang.

“There will be no use of tear gas today,” he said. “In every area where there has been confrontation, we will let them in if they want.”

Earlier protest leader Suthep Thaugsuban had told his supporters to storm the building that protesters had vowed to seize as part of a campaign to topple the government of Prime Minister Yingluck Shinawatra.

Protesters who have occupied other key government buildings, including the finance ministry, for days were ordered not to vandalise offices but to instead cripple the workings of the government.

The police decision to bow to the protesters came hours after a trusted ally of exiled former prime minister Thaksin Shinawatra took charge of defending the government, after Ms Yingluck said she was willing to resign or dissolve parliament to end the crisis.

Surapong Tovichakchaikul, a deputy prime minister and foreign minister who has close connections to Thaksin, replaced a senior police general as head of a unit handling the crisis.

Thaksin, a former policeman and then telecommunications billionaire, has made no public comments about the protests from Dubai, where he has been living to avoid a two-year jail sentence for corruption in Thailand.

But Ms Yingluck, who is his younger sister, has appeared rattled in public appearances after having to flee a police compound last Sunday that was stormed by protesters.

“I won’t make myself a problem. If there is anything I can do to make people happy, I am willing to do it, to resign or to dissolve the House (parliament),” Ms Yingluck said.

“But as Prime Minister what I am able to do must be done under the constitution.”

Ms Yingluck again ruled out a demand by Mr Suthep  to dismantle her administration and allow Thailand’s democratic system to be replaced by a council of appointees who would run the country.

“I can’t really find any law to justify it,” she said.

Although protesters were celebrating their victory, police stepped up their pressure on Mr Suthep, issuing a new arrest warrant on treason charges which are punishable by death or life imprisonment.

Mr Suthep, already facing murder charges over ordering a military crackdown in 2010 when he was deputy prime minister in the previous government, goaded police to arrest him.

He said if they don’t he will give himself up after he had eliminated what he calls the “Thaksin regime".

The easing of tensions came before the 86^th birthday on Thursday of revered King Bhumibol Adulyadej, a day on which Thais show respect for the world’s longest-serving monarch.

The government announced that it had ordered the police to back away to avoid more violence.

"The protesters said they want to seize government buildings, but the government doesn't want to see any fighting or confrontation so we've ordered the police to back off," said government spokesman Teerat Ratanasevi.

Thailand’s powerful military claims it is remaining neutral in the crisis but army officers had been urging police not to use violence against the protesters, including tear gas.

“There is a political problem that needs to be solved by political means,” army chief Prayuth Chan-ocha said on Tuesday. “However we are monitoring from a distance.”

The number of protesters on the streets on Tuesday had been well below the estimated 30,000 that were dispersed from protest sites last Sunday but hardcore elements had shown no sign of giving up.

Four people have been killed and almost 100 injured in the violence.