By raising the stakes in the stand-off, 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 organising the protests to press for greater electoral reforms, would welcome an opportunity to speak to a Chinese central government official, said Lester Shum, vice secretary of the Hong Kong Federation of Students, at a news conference.
“However, we ask them to come to the square and speak to the masses,” Mr Shum said. “This is a movement of Hong Kongers and not led by any specific group.”
Mr Shum demanded that Mr Leung resign by the end of today. He said there was “no room for dialogue” with Mr Leung because he ordered police to fire tear gas at protesters over the weekend, after the street protests started on 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 would not 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 do not 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, protesters kept behind police barricades heckled Mr 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 Mr 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”.