Medical staff members inquire about a patient at a quarantine and isolation center in Johannesburg, South Africa, July 3, 2020.Photo:Xinhua

China's consulate in Lagos, Nigeria issued on Friday a notice warning local Chinese nationals of increasingly frequent kidnapping and robberies as the African economy suffers from COVID-19.

The notice came on the day Bloomberg reported that four Chinese nationals working at a construction company in Akamkpa district of the Cross River state were kidnapped by gunmen local time Wednesday evening. One police guard was reportedly killed in the incident, the report said.

The notice did not mention the incident.

Cross River state police department declined to comment on the incident when reached by the Global Times on Friday.

On Thursday, according to an official release by the Chinese consulate, Consul General Chu Maoming phone called Cross River state governor Benedict Ayade. 

Chu urged authorities in the Cross River state to provide convenience to Chinese nationals and Chinese-funded firms there, and to take effective measures to protect Chinese nationals' legitimate rights.

Ayade said the state government attaches high importance to relations with China, and vowed to protect Chinese nationals' safety and well being. 

A source at the Nigerian capital city of Abuja told the Global Times on Friday that the Cross River state is a safer zone in the country. 

However, abductions of Chinese nationals or rich Nigerian citizens have been on the rise as the economy was significantly affected by the COVID-19, the source said.

Kidnapping has become a business with a complete chain. As long as the kidnappers receive the ransom, which is about 100,000 yuan ($14,260) for each victim, the abductees would be safely returned, the source said.

Police rescue operations rarely succeed--next to never--the source noted. And "the money would be paid by the employers." 

No group has taken responsibility for the incident yet, Bloomberg reported.