The tourists were aboard a Kenya Airways flight from Liberia's capital, Monrovia.

Sierra Leone's Civil Aviation Authority said in a statement that the airline's station manager alerted authorities at Freetown International Airport about a passenger who exhibited symptoms of coronavirus.

It said the four were denied disembarkation on "public health grounds". They left Sierra Leone on a Kenya Airways plane to an undisclosed destination.

"The remaining passengers were allowed to disembark and quarantined as current health precautionary measures demand," the statement said.

There are no confirmed cases of coronavirus in Sierra Leone.

Several African states have imposed far-reaching travel restrictions to curb the spread of the virus.