More than 215,000 people have signed a petition urging French officials to let more doctors prescribe the anti-malaria drug chloroquine for coronavirus patients, a controversial proposal that has divided health experts worldwide.

Support for the treatment has gained ground as doctors try to keep the COVID-19 outbreak from overwhelming hospitals, with some saying early use of chloroquine and similar treatments could keep symptoms from worsening to the point that intensive care is needed.

The French petition on the Change.org website was launched Friday by a group of doctors including Philippe Douste-Blazy, a cardiologist and former French health minister.

On Monday, three of France's most respected doctors penned an open letter backing chloroquine use despite the absence of randomised and peer-reviewed studies on its efficiency. In the absence of anti-virals for the new coronavirus, "we think it is legitimate, given preliminary results, to implement a new strategy," the doctors wrote in Le Figaro newspaper.

The French debate was fuelled by "favourable" findings from a microbiologist who has been treating dozens of patients at the hospital department he runs in Marseille. Didier Raoult's results, however, have been criticised by other doctors who warn of potentially dangerous side effects, and last month France issued a decree against prescribing chloroquine to all but the most severe COVID-19 cases.

US President Donald Trump has cited Raoult's work to push for chloroquine use despite reticence from his own health advisers, asking "What do you have to lose?" at a briefing in Washington on Sunday.

France's Health Minister Olivier Veran on Saturday again urged caution, saying initial results from clinical studies on chloroquine and other potential coronavirus treatments would be available in the coming days.