US President Donald Trump has said he is taking hydroxychloroquine - which health officials have warned may be unsafe - to ward off coronavirus. Photo: BBC

Speaking at the White House, he told reporters he started taking the malaria and lupus medication recently.

"I'm taking it for about a week and a half now and I'm still here, I'm still here," he said.

There is no evidence hydroxychloroquine can fight off coronavirus, though clinical trials are under way.

Asked on Monday what was his evidence of the drug's positive benefits, Mr Trump said: "Here's my evidence, I get a lot of positive calls about it."

The president - who has repeatedly touted hydroxychloroquine - suggested many medical workers were also taking the drug.

"You'd be surprised at how many people are taking it, especially the frontline workers before you catch it, the frontline workers, many, many are taking it," he told reporters. "I happen to be taking it."

The Centers for Disease Control (CDC) says there are no approved drugs or therapeutics to prevent or treat Covid-19.

The US Food and Drug Administration (FDA) last month issued an advisory that hydroxychloroquine has "not been shown to be safe and effective".

It cited reports that the drug can cause serious heart rhythm problems in Covid-19 patients.

The FDA warned against use of the medication outside hospitals, where the agency has granted temporary authorisation for its use if clinical trials are unavailable.

When asked whether the White House physician recommended he start taking the drug, Mr Trump said he himself had asked about it.

"I asked him, 'what do you think?' He said, 'well, if you'd like it', I said, 'yeah, I'd like it.'"

The president said he had "zero symptoms" of the novel coronavirus and is being tested frequently. He added that he has been taking a daily zinc supplement as well.

Mr Trump also told reporters on Monday that hydroxychloroquine "seems to have an impact".

"And maybe it does, maybe it doesn't, but if it doesn't, you're not going to get sick and die."

He added: "I've heard a lot of good stories and if it's not good, I'll tell you right I'm not going to get hurt by it."

The president dismissed reports of severe side effects from hydroxychloroquine, saying the "only negative" he heard about was from one study where the drug was administered to "people in extraordinarily bad condition".

He also claimed that the "very unscientific report" was conducted by "people that aren't big Trump fans".

Mr Trump was apparently referring to a preliminary study from April of Covid-19 patients in US government-run hospitals for military veterans that suggested hydroxychloroquine had no benefit and may have even caused a greater rate of deaths.

"I get a lot of tremendously positive news on the hydroxy, and I say...what do you have to lose?" the president told reporters. "At some point, I'll stop."

Mr Trump spent weeks pushing the drug as a potential cure or preventative for Covid-19, despite the cautionary advice of medical professionals in his administration.

The drug has the potential to cause side effects, including symptoms of heart failure, suicidal thoughts and signs of liver disease, according to doctors.

Last month, the American Medical Association, American Pharmacists Association and American Society of Health-System Pharmacists issued a joint statement opposing the use of hydroxychloroquine, among other drugs, for Covid-19 prevention.

They said the drug should be used if at all "with extreme caution".

Two recent studies, each involving around 1,400 Covid-19 patients in New York, did not find any benefits from hydroxychloroquine.

Another study by French researchers involved 84 hospital patients taking the drug and 97 others who received standard care. It concluded hydroxychloroquine had no impact for better or worse.