The Post-Courier newspaper, citing local police, said the killings began at dawn on Sunday in the Wapenamanda District of the Enga Province.
They involved the Ambulin and Sikin tribes as well as their allies, it said.
Police told the Post-Courier they retrieved some 64 bodies from the roadside, grasslands and hills of Wapenamanda by Monday morning.
Rival factions used “high-powered guns”, such as AK47 and M4 rifles in the battles, the newspaper reported. The death toll is expected to rise, it added.
The Australian Broadcasting Corporation (ABC) said the violence involved the same tribes that were responsible for clashes that killed 60 in Enga Province last year.
“This is by far the largest [killing] I’ve seen in Enga, maybe in all of Highlands as well, in Papua New Guinea,” said George Kakas, a senior officer in the country’s police force.
“We are all devastated, we’re all mentally stressed out,” Kakas told the ABC. “It’s really hard to comprehend.”
The AFP news agency said police received graphic videos and photos from the scene, showing stripped and bloodied bodies lying by the side of the road and piled up on the back of a flatbed truck.
The agency said the military has deployed about 100 troops to the area but that their impact has been limited, with the security services remaining outnumbered and outgunned.
In the capital Port Moresby, opponents of Prime Minister James Mara’s government called for quick action, including the deployment of additional troops to the area.
“We call on the government to immediately establish where the guns and bullets are coming from to fuel this senseless violence,” they added in a statement, according to the Post-Courier.
“That is very disturbing the news that has come out of Papua New Guinea,” he said in a radio interview on Monday.
“We’re providing considerable support, particularly for training police officers and for security in Papua New Guinea.”
