Authorities in China are strengthening border management to stem the importation of COVID-19 through illegal entry channels as the virus continues to spread around the world.

In addition to implementing measures including nucleic acid testing and centralized quarantine for inbound illegal entrants, China has recently taken temporary measures to restrict the entry of foreigners with valid Chinese visas or residence permits to contain the increasing risk of imported infections from abroad.

Authorities in Xiamen, Fujian province, issued a circular on March 31 to strictly prevent the importation of COVID-19 through illegal entry channels by sea.

People who illegally cross the nation's borders or organize and transport others to do so will be investigated, it said, as will enterprises or individuals who harbor, conceal, transport or employ illegal entrants.

According to the circular, illegal entrants could receive mitigated punishment, or even be exempted from punishment, if they voluntarily turn themselves in to public security organs or other competent authorities and truthfully state the facts of their illegal passage across the border.

The circular also encourages the public to report the organizers, participants in illegal entry activities and those who take in illegal entrants.

People can report information by dialing 0592-5781666. Those who provide effective clues or assistance in solving an illegal entry case will get a 10,000 yuan ($1,400) award. Further, those who helped find illegal entrants will be rewarded with 2,000 yuan, it said.

By Wednesday midnight, a total of 841 imported infected cases had been reported on the Chinese mainland.

Also as of Wednesday midnight, Fujian had reported 49 imported confirmed cases and three suspected cases, according to Fujian health authorities' data.

The public security authorities in Quanzhou, Fujian, on March 28 also issued a circular to warn about illegal entry and to encourage the public to report information about such cases as well as people who fail to follow the regulations of medical quarantine and deliberately evade health management.

Earlier in March, 13 foreign nationals climbed mountains and illegally crossed the border into Bainan township in Baise city, Guangxi Zhuang autonomous region. They were immediately repatriated by the border authorities, according to a statement from the website of the Communist Party of China Central Commission for Discipline Inspection and the National Supervisory Commission.

The township has set up 83 informants' boxes and 17 border surveillance stations, and the villagers have been encouraged to report illegal entry activities. Fourteen discipline inspection and supervision teams have been sent by customs in Nanning, capital of Guangxi, to monitor all ports in the region.

Authorities in Yunnan province also issued a circular on March 31 requiring strict control of nonessential personnel flow in border areas. Ports of entry prohibit the passage of people from third countries, and the issuance of exit and entry documents in border areas is suspended.

The Hekou entry-exit border inspection station in Yunnan province has also strengthened international cooperation with Vietnamese border departments and established a mechanism for the rapid exchange of information among entry-exit personnel at ports, providing sufficient response time for epidemic prevention measures.

Border inspection authorities are also working with local governments, farms and health centers to set up duty stations at key border crossings to check for those entering and exiting illegally to prevent the epidemic from spreading.

According to a statement from the border management detachment team in Xishuangbanna Dai autonomous prefecture in Yunnan on March 29, the team cracked a case in which 56 people were smuggled across the border last month, all of whom were arrested.

Hu Meidong and Shi Ruipeng contributed to this story.