Student leaders of pro-democracy protests in Hong Kong warned Wednesday that if the territory’s leader doesn’t resign by the end of Thursday they will step up their actions, including occupying several important government buildings.

By raising the stakes in the standoff, the protest leaders are risking another round of confrontation with the police who are unlikely to allow government buildings to be stormed. It also puts pressure on the Chinese government, which has so far remained mostly silent and preferred to let Hong Kong Chief Executive Leung Chun-ying deal with the crisis.

The student leaders, who have played a key role in organizing the protests to press for greater electoral reforms, would welcome an opportunity to speak to a Chinese central government official, Lester Shum, vice secretary of the Hong Kong Federation of Students, said at a news conference.

“However, we ask them to come to the square and speak to the masses,” Shum said. “This is a movement of Hong Kongers and not led by any specific group.”

Shum demanded that Leung resign by the end of Thursday. He said there was “no room for dialogue” with Leung because he ordered police to fire tear gas at protesters over the weekend, after the street protests started Friday.

“Leung Chun-ying must step down. If he doesn’t resign by tomorrow we will step up our actions, such as by occupying several important government buildings,” he said, adding that demonstrators won’t occupy “essential” government offices, such as hospitals and social welfare offices.

The protesters oppose Beijing’s decision in August that candidates for the territory’s top post in inaugural 2017 elections must be approved by a committee of mostly pro-Beijing local elites. The protesters don’t want such restrictions and see China as reneging on a promise that the chief executive will be chosen through “universal suffrage.”

The demonstrations pose the stiffest challenge to Beijing’s authority since China took control of the former British colony in 1997.

Earlier Wednesday, a holiday, protesters kept behind police barricades heckled Leung as he attended a flag-raising ceremony on China’s National Day, which marks the founding of communist China in 1949. Hundreds of them yelled at him to step down, then fell silent and turned their backs when the ceremony began.

China’s government has condemned the student-led protests as illegal. President Xi Jinping, who has taken a hard line against any perceived threat to the Communist Party’s hold on power, vowed in a National Day speech to “steadfastly safeguard” Hong Kong’s prosperity and stability.

Agnes Chow, another student leader at the news conference with Shum, said she hoped that Beijing would look past the flag ceremony and see “the anger and frustration of the Hong Kong people and that we don’t have our basic democratic rights.”

Given the holiday, the protest numbers swelled Wednesday to tens of thousands, including many families with children, couples, students, retirees and foreigners who live in the city of 7 million. Many thronged a six-lane highway in front of the government headquarters in the Admiralty area, while others gathered in the downtown areas of Causeway Bay and Mong Kok.

“I came out today to support the movement. No student leaders or occupy leaders urged me to come out. I came out on my own,” said Pierre Wong, a 36-year-old IT technician. “I hope there will be democratic reform, instead of using the current framework.”

Throughout the protest zones, volunteers were manning supply stations under canopies to protect against the  sun, handing out water, crackers, umbrellas, rain coats and plastic wrap _ which was also used to protect against the pepper spray and tear gas used by police to try to disperse crowds over the weekend.

In his speech, Leung made no direct mention of the protesters, but he told voters it is better to agree to Beijing’s plans for nominating candidates and to hold an election, than to stick with the current system of having an Election Commission choose the chief executive.

“It is definitely better to have universal suffrage than not,” Leung said. “It is definitely better to have the chief executive elected by 5 million eligible voters than by 1,200 people. And it is definitely better to cast your vote at the polling station than to stay home and watch on television the 1,200 members of the Election Committee cast their votes.”

The growing protests have attracted worldwide attention, with British Prime Minister David Cameron saying he planned to summon the Chinese ambassador to discuss the dispute, saying it is essential that Hong Kong’s people have a genuine right to choose their top leader.

“It is not for us to involve ourselves in every dot and comma of what the Chinese set out,” Cameron said in England. But he added: “I think it is a critical question. Real universal suffrage doesn’t just mean the act of voting; it means a proper choice.”

Chan Kin-man, one of the leaders of another protest movement called Occupy Central, said the protests would continue as long as the Hong Kong government failed to give a satisfactory response to their demands.

“I hope people will understand why the action keeps on escalating. It’s because the government is getting more and more closed without listening to Hong Kong people,” he told The Associated Press in an interview on the street. “If the government can give us a proper response in due course I think we can end the occupation immediately.” (AP)