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Wong Maye-E, Associated Press
Student protesters raise their hands to show their non-violent intentions as they resist during change of shift for local police but backed down after being reassured they could reoccupy the pavement outside the government compound’s gate, Thursday, Oct. 2, 2014 in Hong Kong. Hong Kong police warned of serious consequences if pro-democracy protesters try to occupy government buildings, as they have threatened to do if the territory's leader doesn't resign by Thursday.

HONG KONG — Hong Kong's pro-democracy protesters prepared face masks and goggles and police brought in supplies of tear gas and other riot gear as tensions grew Thursday in a standoff outside of the government headquarters.

Police warned of serious consequences if the protesters try to surround or occupy government buildings. The protesters earlier threatened to do so if the territory's leader, Chief Executive Leung Chun-ying, didn't resign by Thursday. As the day wore on, hundreds of mostly young protesters massed outside Leung's downtown office.

The protesters' calls for Leung to step down are part of broader demands for electoral reforms in the Asian financial center that are the biggest challenge to Beijing's authority since China took control of the former British colony in 1997.

Both the Chinese government and the protesters seemed to be losing patience after a week of street demonstrations.

"It's turning out to be a high-stakes poker game. The stakes are rising," said Willy Lam, a politics professor at the Chinese University of Hong Kong. "Something will have to give because the pressure keeps mounting on both sides to make a compromise."

In a reflection of growing concern in Beijing, the People's Daily, published by China's ruling Communist Party, warned in a commentary Thursday of "chaos" in Hong Kong, and expressed strong support for Leung in his face-off with the protesters, an amorphous movement led mostly by university students.

It said the central government firmly supports the Hong Kong police — criticized for using tear gas and pepper spray on the protesters last weekend — "to handle illegal activities in accordance with the law."

The protesters oppose Beijing's decision in August that all candidates in Hong Kong's first direct election in 2017 for the territory's top post must be approved by a mostly pro-Beijing committee. They accuse the central government of reneging on a promise that the chief executive would be chosen through "universal suffrage."

The students began occupying the area outside the entrance of the imposing government compound housing Leung's office late Wednesday, at times reluctantly moving to allow police vehicles and an ambulance to enter. As Thursday wore on, they grew increasingly resistant to allowing more vehicles in after police hand-carried in tubs labeled "rubber batons" and tear gas.

"I don't think we should let the supplies go through with the ambulance. Who knows if they will sneak in more rubber bullets and tear gas? We shouldn't let them bring in more supplies that will eventually hurt us," said Lap Cheung, 40, a web developer.

It was unclear if the students would press ahead with the threat to occupy government buildings if their demands are not met. Police issued a stern warning that such moves by the protesters would not be tolerated.

"Police emphasize that that is unlawful behavior," they said in a statement. "If they refuse to comply with police advice and warnings, police will take resolute enforcement actions."

The protesters did not say exactly what they planned to do. Joshua Wong, a student activist, urged the public to come out in support.

"I don't know what they mean by what kind of actions they would take to clear us out, but we hope they will not use violence again," Wong said.

Some protesters said they disagreed with the threat to occupy government buildings.

"Getting into a confrontation with police doesn't seem peaceful to me," said Wilson Yip, a 22-year-old recent university graduate. "If they try to force themselves inside and confront police, I don't see what kind of point that would make. It may make fewer people support the protests."

Associated Press writers Elaine Kurtenbach, Kelvin Chan and Louise Watt in Hong Kong, and Didi Tang and news assistant Henry Hou in Beijing contributed to this report.