Mike Roberts and Lydia Bradey were leading eight climbers on an expedition to Mt Carstensz and had reached the village of Pinapa, in the region of Illaga, five days' walk short of base camp.
Those living in the village gave them a friendly welcome, although they searched their belongings thoroughly.
"They were really respectful. That's how it felt to us," Ms Bradey said.
Mr Roberts continued, "Then, basically, this travelling rogue with his band came in. He was very militant and he was extremely aggressive."
The group of Dani tribesmen ordered the climbers out of a building they were in and forced them to sit in the sun.
Their equipment was searched again and spread around, although no money or passports were taken.
"It was just a whole intimidation process. They had machetes, bows and arrows and there were some guns," Ms Bradey said.
There were between 20 and 30 in the group, some of whom set the long, dry grass around the group of climbers on fire.
Ms Bradey believed the tribesmen's goal was not really money.
"I think the goal was just to get us to [leave]."
Mr Roberts said, "I think they had a bit of a deep-seated mistrust and hatred of foreigners, partly to do with all the mining. They think everybody's coming into their land and they want something."
The world's biggest gold mine, the American- and Indonesian-owned Grasberg Mine, is not far from Mt Carstensz.
Mr Roberts said profits from the mine did not filter down to the surrounding tribes.
"Some people get really rich out of the mine but most people don't. So, they are looking at it as a way of getting money. They are also looking at the environmental degradation."
He believed the leader of the group was dressed in a traditional way to make a statement.
"Most of them were wearing western clothing and he was almost completely in traditional dress," Mr Roberts said.
Negotiations ended with the climbers agreeing to pay the tribesmen $US3500 ($NZ4320) and leave.
"We were like, we've got to get out of here. We just need to pay what it's going to take," Mr Roberts said.
The two climbers arrived at Queenstown airport yesterday, only to find their car, which they had left in the car park, had a flat battery.
