JAKARTA (REUTERS) - Indonesia is bracing for its Covid-19 outbreak to get worse after a near vertical climb in cases, a senior minister said on Thursday (July 15), warning that infections had spread faster than anticipated due to the more virulent Delta variant.

The world's fourth most populous country is struggling to slow virus transmission even after imposing its toughest mobility curbs so far. Indonesia began its vaccine rollout in January, but only about 5.8 per cent of its 270 million people have received both shots.

Wednesday's tally of more than 54,000 cases was the latest of many peaks in the past month, and up more than ten times on the number of infections at the start of last month.

Daily infections on Wednesday also surpassed those in India, which has seen a sharp drop in cases after suffering one of the world's worst Covid-19 outbreaks earlier this year.

In a streamed news conference, senior minister Luhut Pandjaitan said daily Covid-19 cases could still climb as the Delta variant, first identified in India, has a two- to three- week incubation period.

"We're already in our worst-case scenario," Mr Luhut said.

"If we're talking about 60,000 (cases a day) or slightly more than that, we're okay. We are hoping not for 100,000, but even if we get there, we are preparing for that," he added.

The government has converted several buildings into isolation facilities, deployed fresh graduate doctors and nurses to treat Covid-19 patients and imported treatment drugs and oxygen, he said.

Indonesia's food and drug agency (BPOM) has authorised the anti-parasitic drug ivermectin for emergency use against Covid-19, a health ministry official told Reuters. BPOM did not immediately respond to request for comment.

While the World Health Organization, as well as European and US regulators, have recommended that the drug should not be used for Covid-19 patients, it is being used to treat the respiratory disease in some countries, including India.

Hospitals in Indonesia's most populated Java island have been deluged in recent weeks, with many people struggling to get treatment and hundreds dying while self-isolating.

Cases and bed occupancy rates also have risen in parts of Sumatra and Kalimantan and more remote regions like West Papua, where health facilities are less equipped to handle an outbreak.

Mr Luhut also said that vaccine efficacy was weaker against the Delta variant that accounted for most infections on Java island, but urged people to get inoculated to help prevent serious illness and death.

The government was analysing the situation and would decide whether to extend the current emergency coronavirus curbs that will expire on July 20, he said.

In a separate statement, the country's Covid-19 task force said there has been a low adherence to health protocols despite the mobility curbs.

The KSPI labour union estimated more than 10 per cent of workers in the manufacturing sector had become infected and many had died.

"This is very worrying and endangering the survival of the business world and the lives of workers," KSPI chairman Said Iqbal told a news conference, warning coronavirus curbs had not stopped factories from continuing to operate at 100 per cent working capacity.