The leaders of Thailand's anti-government protesters said Thursday they will surrender to police after a court dropped treason charges against them, but vowed to continue their occupation of the prime minister's office after posting bail.

Sondhi Limthongkul said he and other leaders of the People's Alliance for Democracy would report to police and apply for bail as early as Thursday afternoon.

Two protest leaders who had been detained were released late Thursday, although they remained charged with less severe but still serious crimes that could result in several years' imprisonment.

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Arrest warrants were issued for the alliance's nine leaders Aug. 27, the day after they led thousands of protesters into the main government office complex, Government House, where they have been camped ever since to demand electoral changes and an end to corruption in Thai politics.

The Appeals Court on Thursday revoked three of the five charges on the warrant: treason, stockpiling of weapons and refusing to disperse. The court said it would issue new warrants with the remaining two charges of inciting public disturbance and illegal assembly — which carry prison terms of seven and three years, respectively.

Protest leaders had said they were willing to fight the charges, except treason which they deemed unjustified.

"We have never accepted the charges of insurrection and stockpiling of weapons in the first place so I am grateful that the court revoked them," Sondhi told protesters from a stage on the Government House lawn. "We will report to the police for the rest of the charges.

"But we will not leave the Government House until they come to disperse us," he said to loud cheers.

Two of the nine protest leaders — Chamlong Srimuang and Chaiwat Sinsuwongse — were arrested recently after leaving the grounds of Government House. The Criminal Court agreed Thursday to their release and waived the $2,900 bail when a senator agreed to act as their guarantor. The others had escaped arrest by refusing to leave the compound, which police have not entered since their sit-in began.

Anti-government protesters have vowed to avenge those killed and injured in clashes this week with the police, which degenerated into the worst political violence in Thailand in more than a decade.

Two people were killed and more than 443 people were injured, including 20 police, in the Tuesday clashes outside the Parliament building, which is near Government House.

Both sides have accused the other of using excessive force.

Hundreds of black-clad doctors and nurses marched Thursday to the national police headquarters, demanding that the government step down to take responsibility for the violence.

Police insist they only used tear gas but questions have arisen over whether tear gas canisters could blow off limbs and toes and feet, some of the more gruesome injuries suffered by protesters.

Police have also faced criticism for mishandling the tear gas and firing it in a way that increased the chances for injuries. The police fired tear gas canisters directly into the crowd, rather than aiming away from the protesters and letting the wind carry the gas into the crowd — as is the general practice with riot police.

Meanwhile, police say they believe some demonstrators were hurt by explosives they themselves were carrying. Protesters said their gathering was peaceful, but many used iron rods, slingshots, firecrackers and bottles to attack police. An AP Television News reporter saw at least three protesters carrying guns.

On Thursday, the Administrative Court issed an order for the prime minister to "adhere to international standards" on crowd control measures.

Authorities must "use soft means before using tough measures when they disperse protesters in the future," the court's statement said. The temporary order will hold until the court has ruled on a lawsuit filed against the government by protesters and senators, charging that riot police had used excessive force.

The protesters say Prime Minister Somchai Wongsawat is a pawn of ex-Prime Minister Thaksin Shinawatra, who was ousted in 2006 by military leaders who accused him of corruption. He now lives in exile. Somchai is his brother-in-law.