Reclusive Turkmenistan on Monday recommended that residents wear masks because of "dust" even as the government insists the country is coronavirus-free.

The announcement came after a World Health Organization delegation arrived in the Central Asian country last week for a 10-day mission examining the response to the pandemic. Turkmenistan is one of a handful of countries yet to declare coronavirus cases.

In a statement published by the state information agency, the health ministry said people should wear masks because of "high concentrations of dust" in the air.

"It is strongly recommended that everyone use personal protective equipment to protect the upper respiratory tract," the ministry said.

It also asked residents to maintain social distancing of at least one metre but gave no explanation. Officials also asked Turkmens not to stand too close to air conditioners after spending time outside, where summertime temperatures regularly exceed 40 degrees Celsius (104 degrees Fahrenheit).

Drivers of public transport and taxi services donned facial protection for the first time last Monday as the WHO delegation arrived. Police had previously been seen discouraging citizens from wearing masks and facial protection was absent from mass government events held in recent months, some of which were attended by thousands of people.

In June, the WHO began recommending masks for public transport and other situations where physical distancing is impossible. Last month the foreign ministry dismissed as "fake news" a US embassy health alert warning Americans over potential coronavirus cases in the country.