A Pakistani refugee who spent more than four years in detention on Manus Island will challenge Papua New Guinea’s light heavyweight boxing champion for a title on Saturday evening.

Ezatullah Kakar will take on 37-year-old PNG champion John Korake in the main fight at the newly formed Oceania professional boxing championship in Port Moresby.

Kakar, a 26-year-old former champion kickboxer and mixed martial arts competitor, said he is fighting on behalf of his fellow detainees on Manus Island and other refugees and asylum seekers on Nauru, sent there under Australia’s offshore processing system.

“After I left Manus almost one year ago I’ve been in Port Moresby. I’ve had two fights and this is my third fight for the title with the PNG champion. I’m very positive I can go well, that I can get to him very easily. I believe in myself and my training and my work.”

Kakar hoped to go on to challenge the New Zealand and Australian title holders, and pledged to fight for PNG if he won.

“Today I have the chance to talk to politicians and everybody,” he said.

“After the fighting in the ring I will speak and use my words to speak to the politicians who are coming. I will show them and I will tell them, that no politicians ever came to Manus and now they are sitting here. In six years they didn’t speak for anyone in the centre.”

Under an agreement between Australia and Papua New Guinea thousands of asylum seekers have been detained and processed on Manus Island over the past six years. The system has been widely criticised by human rights groups, international governments and NGOs.

After the PNG supreme court declared the detention unconstitutional, the two governments embarked on a shutdown process, culminating it the decommissioning of the centre late last year. However hundreds of men refused to leave, citing safety fears in the Manus community.

Kakar remained at the centre on Manus Island throughout the standoff, and collected food and medical supplies from outside the centre until they were forcibly evicted.

“In the last days, on Manus Island, it was very hard,” he said.

Kakar has been supported by Father Dave Smith, an Australian Anglican priest who campaigns for refugees detained offshore and who visited Manus Island during the standoff.

Smith said Kakar felt Manus Island had made him tough.

“Not hard in a nasty sense, but he feels he’s bulletproof after the pain he’s gone through,” Smith told Guardian Australia.

“Thanks to the Australian government he’s become a very tough guy. He was becoming a prominent athlete in Pakistan which is why the Taliban started to take exception to him,” he said.

Smith said Kakar had not had a training routine on Manus, and very little of one in Port Moresby, describing boxing gyms without gloves. He and Kakar had trained together and Smith was scheduled to fight an undercard bout against PNG competitor, Luke Baro.

“It’s going to be hard going for [Kakar], if he does he wants to go on from here to fight Lucas Browne in Australia, to make the big time, for Manus, for Nauru, for all of us,” said Smith.

“I think [this fight] is certainly a big deal for Ezatullah and the men of Manus.”