Singapore on Wednesday approved the use of Gilead Sciences Inc's antiviral drug remdesivir for the treatment of severely ill patients with COVID-19 infection.

Remdesivir is the first drug shown to be effective against the novel coronavirus in human trials, with South Korea, Japan, India and the United States having already approved the drug for emergency use.

Singapore's Health Sciences Authority (HSA) said the conditional approval would allow treatment of adult patients if they have low blood oxygen levels, require supplemental oxygen or intensive breathing support.

"Although the data on its efficacy and safety is very limited at this point in time, HSA has expedited the review of remdesivir given the urgent public health need during the COVID-19 pandemic," HSA said in statement.

Clinical studies involving the drug are being closely watched as nations look for treatments for the disease that has infected more than 7 million people and killed over 400,000 globally.

Tiny city-state Singapore has nearly 39,000 COVID-19 cases, one of the highest tallies in Asia due to mass outbreaks in cramped migrant worker dormitories, but only 25 people have died and only three patients are currently in critical condition.

Remdesivir prevented lung disease in macaque monkeys infected with the new coronavirus, according to a study published on Tuesday. In a U.S.-run clinical trial released in late April, remdesivir reduced hospitalization stays by 31%, or about four days, compared to a placebo.