Customs in Shenzhen, Guangdong province, has intensified efforts to prevent the novel coronavirus from being imported amid a surge in COVID-19 cases in Hong Kong, which neighbors the city.

The number of people entering the Chinese mainland via Shenzhen Bay Port has increased sharply over the past few days, prompting customs in the city to intensify inspection and quarantine efforts at the port, Shenzhen Customs said in a statement on Thursday.

Another 67 confirmed COVID-19 cases were reported in the Hong Kong Special Administrative Region as of 4 pm on Thursday, including 63 locally transmitted cases, the highest number of newly reported cases in a single day since the end of January, according to the region's health authority.

Of the newly confirmed cases on Thursday, the source of 35 were unknown, it said.

Facing the severe challenges, Shenzhen Customs has been closely tracing fluctuations of the epidemic globally and guided ports to take more precise measures for epidemic control and prevention, said Lin Lin, an official with customs.

Existing measures such as temperature and coronavirus nucleic acid testing for every inbound passenger has been strictly enforced, and all inbound passengers are bound to a 14-day isolation, except for passengers who met certain conditions such as students who hold certificates to prove they tested negative for the virus within the past week.

Customs has also increased staff on duty to cope with increasing numbers of passengers to reduce their stay at the port, he said.

COVID-19 has been well under control on the Chinese mainland over the past few months due to effective epidemic prevention and control measures. Only one new confirmed case was reported on Wednesday on the Chinese mainland, according to the National Health Commission.

Recently, about 3,000 passengers have been arriving in Shenzhen daily via the Shenzhen Bay Port, a major route for people coming in from Hong Kong. Before the latest COVID-19 outbreak in the SAR, there had been between 200 and 300 passengers entering each day, according to a report on Thursday by local newspaper Shenzhen Economic Daily.

The number of arrivals in the port has significantly increased since Monday, causing the port to run at full capacity. The port authority has increased the number of vehicles and designated hotels to transfer and isolate inbound passengers, the report said, citing Peng Yaojiu, an emergency management official in Shenzhen's Nanshan district.

All the designated venues for isolation in Shenzhen are operating at full capacity, and passengers whose destinations are outside Shenzhen have been transferred to nearby Dongguan city, with a shuttle bus running between Dongguan and the port every 15 minutes, the report said.