The United Nations has "unequivocally" condemned the escalation of violence across the Highlands of Papua New Guinea which erupted during the national election.

It is calling for an "immediate cessation" of the violence amidst a deteriorating security situation as polling draws to a close in the Highlands region as well as a "swift investigation' and the prosecution of those responsible.

Acting UN coordinator Dirk Wagener said he was "deeply concerned over allegations of the brutal killing of dozens of civilians, reports of heinous sexual violence against women, including at least eight girls, and estimates of several thousand people, mostly women and children, displaced".

"This unmitigated violence shows utter disregard for human rights, and the rule of law," he added.

According to reports, the protracted election process has been marred by allegations of ballot tampering, and ballot box theft in some provinces has provoked public frustration and increased tensions.

Poor organisation, planning, and underlying clan rivalries have also been cited as factors fuelling instability during the voting process, where the winners in many seats have already been declared.

In some areas, the violence has been so severe, it has reportedly led to concerns that the entire democratic process could be derailed.

"Families in many districts are living in fear due to widespread violence in their communities", the UN team in PNG said.

The violence in the Highlands, has already forced an estimated 3000 people in Enga alone, to flee their homes and has caused damage to schools and medical facilities, while businesses and markets have also temporarily closed, the UN statement added.

Some roads have been deliberately cut off through the digging of trenches and destruction of bridges, resulting in disruptions in the delivery of goods and services to these communities, which are now experiencing shortages of food, fuel, medicines, and other critical supplies.

Wagener urged all parties to immediately cease all fighting and called on authorities to fully investigate.

"I wish to underline that the State of Papua New Guinea has a responsibility to uphold the rule of law and ensure the safety of all persons and property, particularly its most vulnerable members of society", he said.

People immune to the violence

RNZ Pacific's PNG correspondent believes people are now becoming used to violence during election.

Scott Waide said the violent extremes reflected a wider public frustration in a poorly planned and managed election.

He told Pacific Waves the three weeks of voting have been seriously affected by the burning or theft of ballot boxes, and violent tribal fighting, especially in Enga Province.

Waide said many of the people killed were women.

"A lot of women who were killed, a good number of women killed within the church area.

"That kind of violence is very worrying in Papua New Guinea. A lot of people have been kind of used to seeing trouble in that part of the region but large number of people being killed in one go is very, very upsetting."

Violence could extend voting in some areas

The election may be extended, in some areas, for another day or two, after logistical complications delayed voting in Western Province.

Three weeks of voting is due to finish on Friday, with the writs due to be returned on 29 July.

Waide said polling in Western Province has often been a challenge, with officials forced to travel long distances on foot, carrying ballot boxes, which cause delays in polling.

He said polling extensions were also likely for other reasons, such as voter protests.

"Frustrated voters actually packed food in one of the ballot boxes and sent it back to polling officials because they said we haven't received any services in the last five years so this is our statement send it back to the polling teams because if polling boxes can come to our area why can't services? So yes, polling may be extended in some areas."