Unrest in Papua New Guinea could prove to be a serious challenge for Australia but it is unlikely to significantly affect regional security, experts say.
PNG's defence force has been called in to restore order as rioting and looting tears through Port Moresby after a peaceful demonstration outside parliament over a payroll issue for public servants deteriorated.
At least 15 people have died across the capital and the second-largest city of Lae, according to the ABC.
AAP has contacted PNG authorities for confirmation.
The violence was against a backdrop of "long-simmering" discontent around social and economic factors, ANU academic Sinclair Dinnen told AAP.
"And the evident failure of the political system and elites who run it to deliver development and services to the bulk of the population," he said.
"(It's) an extremely serious challenge for Australia given its strategic and other interests in PNG and, of course, the recent security agreement between Australia and PNG."
But the unrest was unlikely to affect broader regional security if it was quelled reasonably quickly with previous events in the Solomons and Tonga remaining localised, Pacific affairs expert Anthony Regan said.
"It doesn't necessarily have a particularly big effect (on the region)," he told AAP.
"Some other big worries are the extent of the looting and shutting down of normal market activities, it's going to make people really struggle to find food.
"That is going to be a real concern."
No Australians have been reported caught up in the violence as authorities work to account for citizens.
The Australian High Commission has heightened security measures and staffing levels have been reduced because of the situation.
Tensions had subsided after more police were flown into Port Moresby, PNG Prime Minister James Marape told reporters on Thursday.
"Police were not at work yesterday in the city and people resorted to lawlessness," he said.
No calls for assistance have been sent to Australia but the government maintained a good relationship with PNG, Prime Minister Anthony Albanese said.
"Our high commission in Port Moresby are keeping a very close eye on what is occurring there, making sure that Australians are looked after," he told reporters in Victoria.
"We continue to urge calm at this difficult time."
But even if PNG does request assistance, there would be "several looming challenges" including command and co-ordination with local police, Pacific security expert Jose Sousa-Santos wrote on social media.
Members of the police force were enforcing the law with assistance from the defence force but tensions remained high and the calm could change very quickly, the US embassy in Port Moresby said.
No deaths of citizens had been reported but some were slightly injured, China's embassy said in a statement warning people to step up safety measures.
with Reuters
