Paris police have detained two people on suspicion of hoarding face masks in defiance of a government decree ordering such products be turned over to authorities during the coronavirus outbreak, prosecutors said Friday.

So far four inquiries have been opened in the French capital after checks carried out since President Emmanuel Macron ordered the requisition of face masks in early March.

One in custody is a manager at a drugstore in the posh 16th district of the French capital, the other works at a travel agency where stocks of masks as well as sanitising hand gels were found.

"Pharmacists and drugstore managers need to know that we will be extremely vigilant and that we will prosecute," chief Paris prosecutor Remy Heitz told AFP.

He added that a worker at an organic grocery store in the Belleville neighbourhood was also facing prosecution after he was caught selling a stock of more than 15,000 face masks along with around 250 bottles of fake hydroalcoholic hand gel.

A nationwide shortage of masks has the authorities racing to secure supplies for doctors and hospital workers ahead of an expected surge in coronavirus patients in the coming days.

The government has said 30 million surgical masks will be delivered to hospitals, health clinics and pharmacies in the coming days, and China this week sent France some one million masks to help cope with the crisis.

French health officials have expressed exasperation that many people are wearing masks for their trips outside the house, ignoring repeated advice that they are not needed for healthy people.

Some hospitals have also reported thefts of thousands of masks since the outbreak.