Fifteen people were killed in widespread looting and arson in Papua New Guinea, Australian state broadcaster ABC reported on Thursday, as the South Pacific country's prime minister appealed for calm following a day of protests that turned ugly, Paralel.Az reports citing Reuters.

Eight people died in riots in the capital Port Moresby while a further seven were killed in Lae, in the country's north, the ABC reported, citing an update from police.

A police and public sector protest on Wednesday over a pay cut that officials blamed on an administrative glitch descended into lawlessness over the day, with TV footage showing thousands in the streets of Port Moresby, many carrying what appeared to be looted merchandise as black smoke billowed over the city.

Papua New Guinea Prime Minister James Marape told a news conference on Thursday tensions in the capital had subsided, with extra police being flown in to maintain order.

"Police were not at work yesterday in the city and people resorted to lawlessness, not all people, but in certain segments of our city," he told a news conference on Thursday.

The United States embassy in Port Moresby said police had returned to work, but that tensions remained high.

"The relative calm can change at a moment's notice," it said in a statement, adding it had received reports of violence in several other areas of the country.