Hong Kong: Hong Kong announced new curbs on rail travel on Sunday ahead of the latest in a series of planned protests targeting the airport after a night of widespread violent street clashes in the Chinese-ruled territory.

Anti-government protesters have targeted the airport before, occupying the arrivals hall, blocking approach roads and setting street fires in the nearby town of Tung Chung.

“The airport is still the most important asset to the government," said a 23-year-old protester on Saturday who only gave her name as Kay. "We will adopt hit-and-run tactics and each time help us to gain experience. That’s why I am still calling people to the airport."

Sunday's protest is due to start at noon.

The Airport Express train, which takes passengers under the harbour and across a series of bridges to the airport, built on reclaimed land around an outlying island, will only allow passengers to board in downtown Hong Kong on Sunday, not on the Kowloon peninsula, the Airport Authority said. Only people holding tickets would be allowed to enter the terminal, it said.

"There are calls online for using fake boarding passes, fake air tickets or fake flight booking information to enter the terminal buildings ... The Airport Authority reminds that such behaviour could amount to forgery or using false instrument," it said in a statement.

The violence has hit pockets of Hong Kong at different times over more than three months, allowing life to go on as normal for the vast majority most of the time.

But pictures of petrol bombs and street clashes broadcast worldwide present a huge headache for Beijing just days ahead of the 70th anniversary of the founding of the People's Republic on October 1.

The Hong Kong government has already called off a big fireworks display to mark the day in case of further clashes. China, which has a People's Liberation Army garrison in Hong Kong, has said it has faith in Hong Kong leader Carrie Lam to solve the crisis.

Police fired tear gas to disperse pro-democracy protesters who threw petrol bombs in two new towns on Saturday after pro-China groups pulled down some of the "Lennon Walls" of anti-government messages. There were violent clashes elsewhere in the city.

Police condemned the violence and said there had been many serious injuries in fights between people of "different views".

"They threw petrol bombs at police vehicles and police officers, and even attempted to snatch the revolver of a police officer," police said in a statement on Sunday.

The protests picked up in June over legislation, now withdrawn, that would have allowed suspects to be sent to mainland China for trial. Demands have since broadened into calls for universal suffrage.

The protesters are angry about what they see as creeping Chinese interference in the former British colony, which returned to China in 1997 under a "one country, two systems" formula intended to guarantee freedoms that are not enjoyed on the mainland.

China says it is committed to the "one country, two systems" arrangement and denies meddling. It has accused foreign governments including the United States and Britain of inciting the unrest.