TENS of thousands of pro- democracy demonstrators have extended a blockade of Hong Kong streets, stockpiling supplies and erecting makeshift barricades ahead of what some fear may be a push by police to clear the roads before Chinese National Day.

Riot police shot pepper spray and tear gas at protesters during the weekend but the activists had almost completely withdrawn from the downtown Admiralty district by last night. However, protesters still occupied an area around the government headquarters.

On the eve of today's ­anniversary of the Communist Party's foundation of the People's Republic of China in 1949, crowds poured into central districts of the Asian financial hub, near where National Day festivities are scheduled to take place. Rumours rippled through the crowds of protesters that police could be preparing to move in again, as the government has promised to go ahead with celebrations.

Student leaders gave Hong Kong leader Leung Chun-ying an ultimatum to come out and address the protesters before midnight last night. They threatened to escalate action in the next few days to occupy more government facilities, buildings and public roads if he failed to do so.

The protesters, mostly students, are demanding full democracy and are calling on Mr Leung to step down after Beijing ruled a month ago it would vet candidates wishing to run for Hong Kong's leadership in 2017.

While Mr Leung has said Beijing would not back down in the face of protests it has branded illegal, he also said Hong Kong police would be able to maintain security without help from People's Liberation Army (PLA) troops from the mainland.

He said: "When a problem arises in Hong Kong, our police force should be able to solve it. We don't need to ask to deploy the PLA."

The protests are widely expected to escalate today to coincide with National Day celebrations.

China rules Hong Kong under a "one country, two systems" formula that accords the former British colony a degree of autonomy and freedoms not enjoyed in mainland China, with universal suffrage set as an eventual goal.

Protesters massed in at least four of Hong Kong's busiest areas, including Admiralty, the Central business district, the bustling shopping district of Causeway Bay and Mong Kok in Kowloon.

Organisers said as many as 80,000 people thronged the streets after demonstrations flared on Friday night and many have slept out for the past four nights, blocking usually busy roads.

Alex Chow, leader of the Hong Kong Federation of Students, said the protests, which began as a gathering of students and the Occupy Central movement, had become much broader and attracted Hong Kongers of all walks of life.

He said: "It has evolved into a civil movement. We can see the Beijing and Hong Kong governments already feel pressure, so the Occupy movement must continue."

People set up supply stations with water bottles, fruit, crackers, disposable raincoats, towels, goggles, face masks and tents, indicating they were in for the long haul.

Some lugged metal road barricades into positions on the edge of crowds, presumably to slow a police advance. In at least one location, several minivans and a truck were parked in rows in an apparent effort to block a road.

At one Mong Kok intersection, six abandoned double-decker buses have been turned into makeshift noticeboards, their windows papered with messages of support such as "Please don't give up" and "CY Leung step down".

Protest organisers urged citizens to donate more yellow ribbons, another symbol of the protests, and goggles to protect against tear gas and pepper spray.

Communist Party leaders in Beijing fear calls for democracy could spread to the mainland and have been aggressively censoring news and social media comments about the Hong Kong demonstrations.