PORT MORESBY, Papua New Guinea - Twenty-four people have died - including two pregnant women - in tribal fighting in Papua New Guinea's highlands, prompting the prime minister on Wednesday to promise swift justice.

Local officials said at least 24 people had been killed in Hela Province, a rugged region in the west of the country, in a three-day spasm of violence between tribes.

Highland clans have fought each other in the country for centuries, but an influx of automatic weapons has made clashes more deadly and escalated the cycle of violence.

"Twenty-four people are confirmed dead, killed in three days, but could be more today," Hela provincial administrator William Bando said on Wednesday. "We are still waiting for today's brief from our officials on the ground."

Bando has called for at least 100 police to be deployed to reinforce about 40 local officers.

The incident has shocked both the country and recently appointed Prime Minister James Marape, whose constituency includes the district where the killings occurred.

A native of Hela, he vowed more security deployments and warned the perpetrators, "Your time is up".

"Today is one of the saddest day of my life," he said in a statement on social media. "Many children and mothers innocently murdered in Munima and Karida villages of my electorate."

In the Karida attack, fighters are said to have hacked and shot six women and eight children - as well as two pregnant women and their unborn children - in a 30-minute rampage.

Local health worker Pills Kolo said it was hard to recognize some of the body parts and posted images of remains bundled together using mosquito nets as makeshift body bags.

Images provided by local police showed the corpses of two children of school age, one with severe head injuries.

Local media reported the attack appeared to be in retaliation for the ambush and murder for six people the day before.

"Gun-toting criminals, your time is up," Marape said. "Learn from what I will do to criminals who killed innocent people, I am not afraid to use strongest measures in law on you."

He noted that the death penalty was "already a law".

It is not clear what prompted the attack, but many fights are fueled by old rivalries prompted by rape or theft, or disputes over tribal boundaries.

In nearby Enga Province, a similar surge in violence prompted the establishment of a makeshift military garrison and the deployment of a company of around 100 government soldiers.

Marape has not yet provided details of the security deployments, but appeared exasperated by the current resources available.

"How can a province of 400,000 people function with policing law and order with under 60 policemen, and occasional operational military and police that does no more than band-aid maintenance?" he asked.

Agencies - Xinhua