Protesters who deliberately drive far below the speed limit on the highway will be arrested for careless or dangerous driving, Hong Kong police said at a media briefing on Friday.

The warning came in response to a new round of online calls to paralyze traffic to Hong Kong International Airport on Saturday — three days after the city's controversial extradition bill was withdrawn.

The attempt to disrupt airport operations is "extremely irresponsible", said Li Kam-piu, acting senior superintendent of Traffic New Territories South. Those who drive slowly to impede others' trips to the airport will be cited for careless driving, which carries a maximum penalty of six months' imprisonment, Li said. A driver who intentionally pulls over their car to obstruct traffic flow will be charged with dangerous driving, with a maximum penalty of three years' imprisonment, Li added.

Radical protesters have ignored a Hong Kong High Court injunction that bans any act that obstructs or interferes with the proper use of the airport, including blocking traffic to the airport.

The Airport Authority sought the injunction on Aug 14 after protesters staged mass sit-ins at the airport, causing the cancellation of nearly 1,000 flights and stranding thousands of passengers.

Last weekend, hundreds of flights were delayed or canceled, leaving lines of people stuck at the terminal sitting on suitcases, while scores of suitcase-toting travelers walked down the highway. Violent clashes and vandalism at train stations to the airport brought Airport Express train service to a complete halt.

In light of the situation, the city's rail operator, MTR Corp, announced the suspension of services at the Airport Express's Kowloon and Tsing Yi stations effective 9 am on Saturday — a request from the Airport Authority.

In an advertisement headlined "Spare our passengers further disruption" in Hong Kong's major newspapers on Friday, the Airport Authority urged demonstrators "not to disrupt the journey of tens of thousands of travelers who use our airport every day."

The Airport Authority has strengthened access control of the terminal buildings amid online calls to sneak into the airport with forged boarding passes and travel documents.

Protesters face up to 14 years in prison if they fake documents to pass airport checkpoints, said Lau Wing-kei, deputy district commander of Airport District. A number of protesters have reportedly disguised themselves as reporters, paramedics or legitimate travelers to gain access to the departure or arrivals halls.

So far, 18 have been arrested since mid-August for their involvement in three unlawful assemblies at the airport, police said at the briefing.

Unauthorized assemblies at the airport in mid-August, which culminated in protesters' violence toward and unlawful detention of two mainland travelers and brought the airport services to a standstill for one day and a half, affected 300,000 passenger trips and caused a loss of cargo valued at an estimated HK$15 billion ($1.9 billion), according to experts from tourism and air freight sectors.