A state in the southern central part of Australia, announced one of the worlds toughest lockdowns on Thursday with even outdoor exercise and dog-walking banned as the state tries to contain a cluster of Covid-19 infections.

South Australia State's premier Steven Marshall said that for six days, only one person from a household will be allowed to leave home each day, and only for essential reasons, authorities said. Schools, universities, cafes and restaurants are already closed, weddings and even funerals are banned and mask-wearing is mandatory in the state which covers some of the most arid parts of Australia.

Twenty-three people in the state capital Adelaide have been infected after a cleaner at a hotel used to quarantine people arriving from overseas was exposed to the virus, and health authorities say the "circuit breaker" measures are necessary to avoid a wider outbreak.

"We want to go hard, go early, but get out of it as quickly as we can," Marshall said adding that the strain of the virus thats circulating is "nasty" as many of those infected are not showing any symptoms. He said it was highly likely to be transmitted from surfaces and that the incubation period was as low as 24 hours.

"Its a real worry, especially because people who become infected are not showing the typical symptoms that we are used to," Marshall added.