Indonesia is bracing for its Covid-19 outbreak to get worse after a near vertical climb in cases, a senior minister said, 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.

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,” Luhut said.