A state of emergency has been declared in Papua New Guinea's capital after at least 15 people were killed in rioting.

More than 1,000 troops are on standby "to step in wherever necessary", Prime Minister James Marape said on Thursday.

Shops and cars were torched and supermarkets looted after police went on strike on Wednesday over a pay cut the authorities say was a mistake.

The unrest follows wider tensions in the Pacific Island nation over rising costs and high unemployment.

"Breaking the law does not achieve certain outcomes," Mr Marape said in a national address. He announced the state of emergency in Port Moresby would last for 14 days.

While most of the violence had been curbed by Wednesday evening, after soldiers were deployed and police resumed duty, the prime minister acknowledged that the situation was "still tense".

The Port Moresby General Hospital confirmed eight deaths in the capital, while another seven people were reported to have died in the city of Lae, PNG's second largest.

The absence of police encouraged people from the capital's outskirts to ransack shops and cause wider destruction, locals told the BBC.

"We have seen unprecedented level of strife in our city, something that has never happened before in the history of our city and our country," National Capital District Governor Powes Parkop said in a radio address on Wednesday, according to a Reuters news agency report.

He said the looting had largely been carried out by "opportunists". Some violence was also reported to have been carried out by police demonstrators.

The unrest was triggered after police and other public servants staged a protest strike outside parliament on Wednesday, after discovering that their wages had been reduced by up to 50% in their latest pay cheques.

In response, Mr Marape said the pay cut was an error due to a computer glitch - which had deducted up to $100 (£78) from the pay cheques of public servants. He said the administrative error would be corrected in next month's payments.

But this answer was not accepted by many protesters, some of whom then tried to push into the parliament building - with footage showing people torching a car outside the prime minister's compound and overrunning a gate.

Many pointed to claims on social media that the government was raising income taxes, an assertion denied by the government.

"Social media picked up on this wrong information, misinformation," said Mr Marape, according to the New York Times, adding that people had taken advantage of police being off the streets.

Port Moresby resident Maholopa Laveil told the BBC that opportunists had ransacked the city, setting many buildings and small shopping centres on fire and stealing cars. The worst of the violence happened during the day.

"We had a lot of fear for people who were working in the shopping centres and offices - there was a lot of glee and excitement from the people who were attacking and entering the shops," he said.

Mr Laveil, who is an economics lecturer at the University of Papua New Guinea, also said most of the people looting appeared to be from the poorer settlements outside the city.

"They had come on when they heard the police had stood down and were not policing the city.

"These are suburbs with really poor people, who don't have jobs and who contribute to a lot of crime and lawlessness in the city. Many have suffered a lot from not being employed - inflation pressures - and they came out in numbers trying to get what they could from the shops nearest to them," he said.

Ambulance officials said they had attended to several shooting injuries, while the US embassy reported shots near its compound.

The Chinese embassy has also lodged a complaint with the PNG government, saying several Chinese businesses were attacked and two Chinese nationals injured.

"The Chinese Embassy in Papua New Guinea has lodged solemn representations with the Papua New Guinea side over the attacks on the Chinese shops," the embassy said on WeChat.

Amid an economic slump in his country that has seen higher inflation and unemployment rates, the prime minister has faced increased pressure and public resentment from many groups.

The political opposition has also been working on a motion to hold a vote of no confidence in Mr Marape, scheduled for February.

"Households are doing it tough, there's growing inequality within urban centres particularly the capital city and we've got a growing number of settlements and high crime rates," Mr Laveil said.

"All of those factors contributed to a perfect storm."