Tens of thousands of students returned to school in Shanghai and Beijing after months of closures as China's major cities gradually return to normality.

Shanghai students in their final year of middle and high school went back to classrooms, while only high school seniors in Beijing were allowed on campus again to prepare for the all-important "gaokao" university entrance exam.

The Bank of Japan ramped up its emergency monetary easing and cut growth forecasts for the world's third-largest economy.

The central bank said it would shift to unlimited government bond-buying and more than double its capacity to purchase corporate bonds and commercial papers -- a move to support financing as the country grapples with fallout from the virus.

Meanwhile, Asian markets rallied as the rate of deaths from the virus sank in several badly hit countries, while leaders stepped up plans to reopen their economies, though oil prices sank with supply glut fears overshadowing output reductions.

"There is no widespread, undetected community transmission in New Zealand," Ardern declared. "We have won that battle."

Nearly two million Australians rushed to download a new smartphone app designed to make coronavirus contact tracing easier, the government said, overlooking privacy concerns in the hope of speeding up the end of social-distancing lockdowns.

An Indonesian official sprays disinfectant at the Kasang Kulim zoo in Riau province, Indonesia, where Bornean orangutans are among animals facing starvation because of a lack of zoo visitors
An Indonesian official sprays disinfectant at the Kasang Kulim zoo in Riau province, Indonesia, where Bornean orangutans are among animals facing starvation because of a lack of zoo visitors AFP / Wahyudi

Health Minister Greg Hunt hailed take-up since the app was released Sunday evening as "extraordinary", saying 1.9 million people had downloaded the program in less than 24 hours.

Thousands have been detained for breaking the rules and some have been handed short jail terms. Authorities have established temporary jails to hold the extra inmates and said at the weekend that the first batch of 58 people had been sent to the prisons.

Thailand recorded nine new infections -- the first time the number of new cases has dropped to single digits since the government declared a nationwide state of emergency over a month ago.

Currently, the country has 2,931 cases of COVID-19, and a death toll of 52.

China's ambassador in Australia has warned that demands for a probe into the spread of the coronavirus could lead to a consumer boycott of Aussie wine or trips Down Under.

Australia has joined the United States in calling for a thorough investigation into how the virus transformed from a localised epidemic in central China into a pandemic that has killed more than 200,000 people, forced billions into isolation and torpedoed the global economy.

Thousands of animals, including Sumatran tigers and Bornean orangutans, are facing the threat of starvation at Indonesian zoos.

More than 90 percent of the archipelago's zoos only have enough feed until mid-May and not enough money to buy more owing to a lack of visitors, according to the Indonesian Zoo Association.

In Afghanistan, President Ashraf Ghani ordered the release of about 12,400 prisoners in an attempt to slow the spread of the coronavirus. Ghani's decree comes on top of an earlier directive to release 10,000 prisoners for the same reason, and was unrelated to ongoing prisoner-swap negotiations with the Taliban.