HONG KONG - In an effort to contain the spread of a novel coronavirus in Hong Kong, the government moved to further tighten border control by requiring all people entering the city from the Chinese mainland to be quarantined for 14 days.

The new arrangement, which also applies to Hong Kong residents, will take effect on Feb 8, said Chief Executive Carrie Lam Cheng Yuet-ngor at a press conference on Wednesday afternoon.

This new measure was introduced after medical experts warned that there was a real risk of the spread of the virus in the communities.

According to Lam, yet unidentified sources of infection for the three latest HK people to have been confirmed as patients indicated the possibility of community transmission.

But she said she remains optimistic that with concerted efforts of the government and society, the city will succeed in fighting the virus.

Lam said the measure would take effect two days later so as to give time to people whose life would be affected by the new arrangement to prepare for the change.

The detailed information related to the measure's implementation will be revealed during a government press conference on Thursday, according to Sophia Chan Siu-chee, Secretary for Food and Health.

Secretary for Labour and Welfare Law Chi-kwong pledged that the government would explore feasible measures to assist cross-boundary employees and caregivers who would be affected by the new arrangement.

Hong Kong so far recorded 21 confirmed cases of the novel coronavirus, which was first discovered in Wuhan in Central China's Hubei province and has infected more than 20,000 people on the Chinese mainland.

Earlier, the government closed down all but three of the border checkpoints. Hong Kong International Airport, Hong Kong-Zhuhai-Macao Bridge and Shenzhen Bay are the only ones that have remained open from Tuesday.

On Tuesday, 28,675 people entered Hong Kong via the Shenzhen Bay and the Hong Kong-Zhuhai-Macao Bridge checkpoints, down 64 percent from Monday. More than 80 percent of them are Hong Kong residents, said Lam.

Airport arrivals fell by 21 percent to 41,137 on Tuesday. The vast majority of them were international visitors, with only 224 of them were from the mainland with Chinese passports.

The government also announced the closure of the Kai Tak Cruise Terminal, where the World Dream cruise ship docked on Wednesday morning. More than 1,800 people on board have been put under quarantine as three passengers were found to have contracted the virus.