Myanmar has imposed mandatory quarantine and coronavirus tests for visitors to its capital city after the country reported dozens more infections on Wednesday and leader Aung San Suu Kyi warned of a "disaster for the country".

Anyone entering the capital, Naypyitaw, where the government is based, will be quarantined, tested, and allowed entry only if their result is negative, according to a government order published on Facebook.

People coming from the country's worst-hit areas will be quarantined in a facility for at least seven days, said the order by the Naypyitaw Council, while others will be allowed to leave earlier if they test negative, Reuters reported.

Myanmar reported its first local transmission in a month in mid-August in the restive western Rakhine state. Since then, the number of cases has roughly doubled to 1,059 infections and six deaths, according to government data.

The majority of the cases and deaths have been in Rakhine, where government troops are fighting ethnic insurgents and authorities have imposed sweeping curbs on internet access.

Most recent infections have been in that state's capital, Sittwe, where officials have imposed a stay-at-home order and a curfew.

Sittwe is also home to camps where about 100,000 Rohingya Muslims have been confined since an outbreak of violence in 2012. Rohingya are mostly denied citizenship and face strict curbs on freedom of movement and access to healthcare.

But infections have been found across the country including in the biggest city, Yangon. Authorities imposed a partial lockdown in parts of Yangon on Tuesday, ordering residents of the worst-hit townships to stay at home other than for essential journeys. Bars and nightclubs have been closed.

Suu Kyi said those who disobeyed instructions would face punishment under the Natural Disaster Law, which carries prison terms of up to a year.

"More strict action will be taken under the Natural Disaster Law. This is a disaster for the country," she said in a video broadcast on Wednesday.

"If the pandemic spreads widely in Yangon, it will be very difficult to provide medical treatment to the people," she said.

Doctors say they fear a major outbreak in the country, which has a health system ranked among the world’s worst after decades of neglect under military rule. Many services are run by volunteers and aid groups.