Hong Kong’s pro-democracy protesters have threatened to occupy key government buildings unless the territory’s top official resigns by the end of the day.
The Chinese government, meanwhile, appeared to be losing patience with the movement.
An editorial solemnly read on state TV said all Hong Kong residents should support authorities in their efforts to "deploy police enforcement decisively" and "restore the social order in Hong Kong as soon as possible".
The Communist Party-run People’s Daily warned of “unimaginable consequences” if the protests persist.
In the biggest challenge to Beijing's authority since China took control of the former British colony in 1997, thousands of demonstrators have clogged the streets of the Asian financial centre since last Friday, demanding freer elections in Hong Kong.
Storming government buildings would risk inviting another clash with police like the one over the weekend. It also would put pressure on the Chinese government, which has backed Hong Kong chief executive Leung Chun-ying’s attempts to end the protests but has not openly intervened.
In Washington, secretary of state John Kerry met with Chinese foreign minister Wang Yi and said the US supports the "highest possible degree of autonomy" in Hong Kong.
He said he hopes Hong Kong authorities exercise restraint and allow the protesters to express their views peacefully.
Mr Wang said the protests are "China's internal affairs" and that no country would allow "illegal acts" against public order.
One of the protest leaders, Lester Shum, vice secretary of the Hong Kong Federation of Students, said there was "no room for dialogue" with Mr Leung because he had ordered police to fire tear gas at demonstrators over the weekend.
“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,” Mr Shum said, adding that demonstrators would not interfere with essential government agencies such as hospitals and social welfare offices.
Chan Kin-man, another protest leader, said the demonstrations will continue as long as the Hong Kong government fails 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 said in an interview on the street.
The protests were triggered by Beijing’s recent decision that all candidates in the inaugural 2017 election for Hong Kong’s top post must be approved by a committee of mostly pro-Beijing local elites.
In a speech early on Wednesday marking National Day, the anniversary of the 1949 founding of Communist China, Mr Leung did not mention the protesters, but told voters it would be better to agree to Beijing's plan and hold an election than to keep the current system, in which an Election Commission chooses the chief executive.
Protesters heckled Mr Leung after he arrived for the flag-raising ceremony. Hundreds yelled at him to step down, then fell silent and turned their backs when the ceremony began.
As the protests have worn on, Beijing’s tone has hardened.
President Xi Jinping, who has acted harshly against any perceived threats to the Communist Party’s hold on power, vowed in a National Day speech to “steadfastly safeguard” Hong Kong’s prosperity and stability.
Turning up the pressure on leaders in Beijing, sympathy protests sprang up in Macau, a former Portuguese colony that China took over in 1999, and in the independently ruled island of Taiwan, which China claims as its own.
The crowds of protesters in Hong Kong swelled to tens of thousands yesterday, a national holiday, 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 district, while others gathered in the central 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.”
Press Association