Buildings were set ablaze and looted some 50 metres down the road from the Salvation Army compound.
The Salvation Army site is manned by an Australian couple, Papua New Guinea Territorial Commander, Colonel Kelvin Alley and Colonel Julie Alley, along with a number of local staff.
In a statement, Colonel Alley said the scene was one of “great devastation”.
“We watched helplessly as vital services in the community burnt to the ground, (were) gutted and are now gone. Services like the medical centre, the dentist and the chemist.”
“These services play a vital role in any community but are a particular loss here where there is great need,” he said.
Kathy Testh, who works at the Mapang Missionary Home a few blocks away, told AAP she woke to hear gunshots.
She said she drove to a meeting, and when she returned the main roads were cordoned off and manned by armed guards, stopping people from entering the area.
Mr Alley said although the situation has now calmed down, the recovery from such an event will be slow.

A man runs through the streets of Port Moresby (Colonel Julie Alley) Source: Colonel Julie Alley
“Almost the entire business block across the road has been destroyed, unnecessarily by raging fires, rampant looting and out of control crowds,” he said.
“That hundreds of people would look past the destruction of so much that was good, just to get their hands on some free goods but at what cost.”