Coronaviruses are a group of viruses ranging from the common cold to SARS -- severe acute respiratory syndrome -- virus, the BBC reported.
The WHO said the new coronavirus has been linked to either Saudi Arabia or Qatar.
One man has been transferred to Britain for treatment.
"Until more information is available, it is prudent to consider that the virus is likely more widely distributed than just the two countries which have identified cases," the WHO said in a statement.
The coronavirus was first detected in September and is genetically distinct from SARS, Medical News Today reported.
"Investigations are ongoing in areas of epidemiology, clinical management and virology, to look into the likely source of infection, the route of exposure, and the possibility of human-to-human transmission of the virus. Close contacts of the recently confirmed cases are being identified and followed up," the WHO said.