Hong Kong police used tear gas to break up anti-government protests on Saturday after some activists threw petrol bombs and bricks.

Police used tear gas after some protesters threw Molotov cocktails and bricks, and others tore up "smart" lamp posts equipped with surveillance cameras. Others had set up roadblocks with bamboo scaffolding.

It was the first use of tear gas in 10 days after a series of mostly peaceful demonstrations in the former British colony.

There were no immediate reports of injuries.

Watch: Hong Kong protesters warn CBC's Chris Brown of tear gas

CBC's team on the ground is in the thick of it during another weekend of protests in Hong Kong. 1:48

The police tweeted at 10 p.m. local time that they would conduct a "dispersal operation," warning nearby residents to keep their windows shut and to stay inside.

"Give me democracy or give me death," was spray-painted on a wall, an illustration of how the demands of the protesters have expanded from the withdrawal of a bill that would have allowed extraditions to China.

The government said in a statement the protesters "posed a serious threat to the safety of everyone" at the scene.

"After repeated warnings to the protesters went futile, police officers have deployed tear gas and minimum force to disperse protesters," it said.

Tear gas floats in the air as demonstrators clash with riot police during a protest at Kowloon Bay in Hong Kong on Saturday. (Tyrone Siu/Reuters)

The airport and the roads and railways leading to it were operating normally despite plans by protesters to implement a "stress test" of transport links after weeks of unrest.

The airport was forced to close for part of last week after protesters thronged the main terminal for several days, grounding around 1,000 flights and occasionally clashing with police.

No sign of let-up

The wider calls for democracy have plunged the city into an unprecedented crisis, posing a direct challenge for Communist Party leaders in Beijing.

A demonstrator throws a piece of brick as they clash with riot police Saturday. (Kai Pfaffenbach/Reuters)

Demonstrators say they are fighting the erosion of the "one country, two systems" arrangement that enshrines a high degree of autonomy for Hong Kong since it was handed back from British to Chinese rule in 1997.

There is no sign of a let-up almost three months after the anti-government demonstrations began. On Friday night, thousands of chanting protesters formed human chains around the city in a peaceful protest dubbed the "Hong Kong Way."

Authorities have so far refused to meet any of the protesters' five key demands, including calls for an independent inquiry into police brutality, a full withdrawal of the extradition bill and full democracy.

Organizers are planning a host of protests in the coming weeks including a mass march, a city-wide strike and class boycotts at universities.

Meanwhile, Global Affairs Canada is advising travellers to exercise a high degree of caution when visiting the region, in addition to warning about an increase in screenings of digital devices at border crossings between Hong Kong and mainland China.

Consulate staffer freed

British consulate staffer Simon Cheng Man-kit was detained for 15 days for violating public security management regulations, police in Shenzhen, across the border from Hong Kong, said on their Twitter-like Weibo account.

Police said Cheng was released as scheduled on Saturday and that his legal rights and interests had been observed. They also said Cheng had confessed to accusations against him, a commonly used comment by Chinese police, even though Cheng was not given a chance to defend himself in court.

Cheng had now returned to Hong Kong, his family said on his Facebook page.

No details were given of his detention, with the Facebook post asking the "media and friends to give them some time and space, and we will explain more later."

Some protesters in recent days had demanded Cheng be released. Britain said it welcomed the news.