Police in Papua New Guinea are investigating multiple killings on the Hiritano Highway near the capital Port Moresby.
The killings reportedly stemmed from an attempted hold-up of a public bus earlier this week.
Police accounts indicate a man from Goilala in Central Province was killed by bushknives when he and others tried to rob a bus carrying bags of betelnut.
Later, in retaliation, Goilala people began stopping buses driving the highway into Port Moresby until they found one with passengers who they decided to attack.
Three men believed to be from the Highlands region were hacked to death and left on the roadside, as other passengers fled in fear.
Police said they were searching for suspects, and had deployed extra personnel to patrol the area and prevent further roadblocks.
The Police Divisional Commander of the National Capital District and Central Province, Anthony Wagambie Jr said the attacks had caused significant disruption to many people from Kairuku, Mekeo, Beraina and Gulf province.
"I appeal to our people living along the Hiritano highway, especially the Goilala people, to allow the free flow of traffic," Wagambie said.
"The Highway belongs to everyone. There are many people being stranded on both sides."
He indicated police would be closely monitoring the traffic going through the area in the coming days, but has appealed to the public to co-operate with the constabulary.
"The province of origin of the threemen who were killed is still unknown at this stage. We expect more information once relatives comne forward after identifying the deceased."