GENEVA, March 26 (Xinhua) -- The World Health Organization (WHO) on Friday said it was concerned about the potential criminal exploitation of the huge unmet global demand for COVID-19 vaccines, warned against counterfeit vaccines and urged people to stick to government-run vaccination programs.

According to WHO Director-General Dr. Tedros Adhanom Ghebreyesus, several ministries of health, national regulatory authorities and public procurement organizations across the world had received suspicious offers to supply COVID-19 vaccines.

The WHO is "aware of vaccines being diverted and reintroduced into the supply chain, with no guarantee that cold chain has been maintained," he said, adding that counterfeit vaccines have been sold on the internet, primarily on the dark web. There have also been reports of "criminal groups" reusing empty vaccine vials.

Also on Friday, the WHO issued an alert for a counterfeit COVID-19 vaccine identified as BNT162b2, which was detected in Mexico in February.

The product was supplied and administered to patients outside authorized vaccination programs, may still be in circulation in the region and continue to be offered to patients outside authorized vaccination programs, the WHO said.

The genuine BNT162b2 COVID-19 vaccine is indicated for active immunization to prevent COVID-19 in individuals older than 16.

"Falsified COVID-19 vaccines pose a serious risk to global public health and place an additional burden on vulnerable populations and health systems. It is important to identify and remove these from circulation," the WHO warned in a statement.

Dr. Tedros urged the public not to buy vaccines outside government-run vaccination programs, and to report any suspicious sale of vaccines to the national authorities, who will report it to the WHO.