The Governor of Papua New Guinea's National Capital District has condemned the violence in the middle of Port Moresby on Sunday afternoon.
People presumed to be supporters of rival election candidates clashed at the Sir John Guise Stadium where votes from the national election were being counted.
The attackers were armed with machetes and other weapons.
There are unconfirmed reports that at least two people were wounded.
The Governor, Powes Parkop, said he was shocked to see such grotesque violence in the country's capital, and in broad daylight.
He said it is totally unacceptable and no justification can be made for such unacceptable behaviour.
Mr Parkop saids last week he requested police increase security in the counting centres as he was concerned about the tension and the security risks, but he said he is not aware that any such efforts were made.
He said those who committed "this grotesque acts of violence must be arrested and charged and if their candidates are also involved in the planning of these act of violence they too be arrested and charged."
Mr Parkop called on all candidates to restrain their supporters and show leadership.
Bishops demand Government return to capital
The Catholic Bishops of Papua New Guinea said, in a statement, due to the volatile situation in Port Moresby, the caretaker Prime Minister, James Marape, and his Cabinet must return to the city, and sort out the problems resulting from the unruly election.
In a statement the bishops said the leaders need to return to supervise the proper completion of the electoral process; to direct the work and the intervention of the security forces; and to guarantee the safety of individuals, public institutions, and businesses.
They said a severe deterioration of events in the National Capital District in the next few hours or days will deprive those currently holding positions of responsibility of any future credibility and trust for the welfare of the country and its citizens.