A US man has died and his wife is in critical condition after ingesting a chemical they believed Donald Trump had touted as a cure for coronavirus .

The unnamed couple watched a White House briefing where the US President incorrectly said that malaria drug chloroquine had been proven effective in treating COVID-19.

"Chloroquine or hydroxychloroquine. Now, this is a common malaria drug," Mr Trump said.

"The nice part is, it's been around for a long time, so we know that if it—if things don't go as planned, it's not going to kill anybody."

President Donald Trump has touted hydroxychloroquine as a potential coronavirus cure. (AP)

Mr Trump has also tweeted about its benefits.

An Arizona woman recalled chloroquine as a chemical in a parasite treatment for her goldfish.

"I saw it sitting on the back shelf and thought, 'Hey, isn't that the stuff they're talking about on TV?'" she told NBC .

The couple in their 60s, who have pre-existing conditions that put them at heightened risk of serious coronavirus , mixed the substance with a liquid and drank it.

Within 20 minutes, they felt seriously ill, and the woman's husband died shortly after arriving at hospital.

'It's not going to kill anybody', said Donald Trump about a drug an Arizona man subsequently took, then died. (AP)

In a heavy enough dose, hydroxychloroquine is used as a chemical to clean fish tanks.

Meanwhile, in Nigeria, three people have overdosed on chloroquine while trying to ward off COVID-19.

"(The World Health Organisation) has NOT approved the use of chloroquine for COVID19 management," the Nigeria Centre for Disease Control tweeted.

"Please DO NOT engage in self-medication. This will cause harm and lead to death."

Prices of the drug have quadrupled in some parts of Nigeria off Mr Trump's recommendation.

There are 30 diagnosed cases of coronavirus in Nigeria at present.

A Nigerian port health official, right, uses a thermometer to screen Ethiopian Airline cabin crews for COVID-19 virus. (AP)

The drug has shown some promise in French trials for killing coronavirus.

But many scientists have questioned the rigour of the experiment.

But because of the severe side-effects of using the drug, human trials have not yet begun.

Doctors warn not to use the drug if pregnant, planning on becoming pregnant or breastfeeding.

Hydroxychloroquine is a common preventative medication for malaria, though it has significant side effects. (AP)

People with liver disease, hearing problems, blood disorders, certain vision problems and many other conditions may be advised against using it.

Hydroxychloroquine has not been approved by America's Federal Drug Agency for use for coronavirus.

Doctors around the world are yet to determine an effective treatment for COVID-19.

Every act of social distancing can have a dramatic impact on the spread of coronavirus. (Australian Government)