Protesters intent on toppling Thailand’s democratically elected prime minister plan to press their struggle again Wednesday with a peaceful march on Bangkok’s national police headquarters, one day after a sudden truce in honour of the King’s birthday this week ended a spate of increasingly fierce street fighting.

The pause in violence came suddenly on Tuesday, when Prime Minister Yingluck Shinawatra ordered police to end their resistance against masked mobs who had begun attacking their positions beside her office compound with homemade rocket launchers and petrol bombs.

The move was timed to coincide with celebrations of the King’s birthday this week, a holiday that holds deep significance in the Southeast Asian nation. It was widely seen as offering demonstrators a face-saving way out of a crisis that has killed four people and wounded more than 256 since the weekend.

But protest leader Suthep Thaugsuban vowed to keep up what has become an audacious struggle to overthrow Ms. Yingluck and keep her brother, deposed former Prime Minister Thaksin Shinawatra, from returning to power.

“You can rest assured that this is a victory that is only partial ... because the tyrannical Thaksin government endures,” Mr. Suthep said.

Ms. Yingluck’s rivals accuse her of being a puppet of Mr. Thaksin, who was ousted in a 2006 military coup and lives in Dubai to avoid a corruption conviction he says was politically motivated. His overthrow touched off a societal schism that has plagued Thailand ever since.

In broad terms, the conflict pits a poor rural majority which largely backs the Shinawatra family against an urban-based elite. The latter camp draws support from the army and staunch royalists who see the Shinawatras, who have won over rural voters with populist policies designed to benefit them, as a corrupt threat to their business interests and the monarchy.

Protesters argue that Ms. Yingluck came to power through her billionaire brother’s money and vote-buying, charges the ruling party denies. Mr. Suthep insists Ms. Yingluck must cede power to an unelected council, but Ms. Yingluck has rejected that demand, which many political observers and Thai academics say is absurd and a threat to the country’s nascent democracy.

Ms. Yingluck’s Pheu Thai party was elected with an overwhelming majority in 2011 and is currently unbeatable at the polls.

Last month, tensions boiled after the ruling party tried to ram an amnesty bill through Parliament that critics said was mainly designed to bring Mr. Thaksin back.

Protesters seized several government ministries and offices last week, and by Sunday they were trying to smash through concrete barriers surrounding Government House, where Ms. Yingluck’s office is located. They fired homemade rocket launchers and petrol bombs at police, who riposted with tear gas, water cannons and rubber bullets.

But suddenly, early on Tuesday, police lowered their shields and walked away from their heavily fortified positions. Bewildered protesters who had been fighting just moments before began climbing over rows of overturned concrete blast walls.

Shortly afterward, thousands of jubilant demonstrators waving the red, white and blue Thailand flag swarmed across the grassy lawn of Government House, snapping photos of themselves with cellphones and screaming “Victory belongs to the people!” Ms. Yingluck was not there at the time.

About 20 soldiers and police guarded a door into Ms. Yingluck’s offices, and protesters did not try to enter. After an hour of speeches and cheering, they all filed back out systematically a highly organized exit which fuelled speculation that a deal at least for now had been struck behind closed doors between the two sides.

Ms. Yingluck and said police had been ordered to avoid clashes so people could peacefully celebrate the birthday of ailing King Bhumibol Adulyadej, who turns 86 on Thursday.

King Bhumibol is a constitutional monarch with no formal political role, but he is considered the country’s moral authority and a unifying figure. Violence on the day of his birth would be a major sign of disrespect.

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