Six prisoners have climbed onto the roof of Perth's Hakea Prison in what is believed to be a protest of last week's not guilty verdict for NT Police Constable Zachary Rolfe over the shooting death of Kumanjayi Walker.

The Department of Justice on Wednesday arfternoon confirmed there were six prisoners on the roof at Hakea Prison in Perth's southern suburbs.

The prisoners climbed onto the roof shortly after 2pm today.

Ngalla Maya chief executive Mervyn Eades said he had been told the prisoners were protesting conditions in the prison, lockdowns, and the Yuendumu trial verdict.

"The boys inside told me - I got a phone call from there," he said.

"They said 'the boys just got on the roof', before they cut the phones off.

"Hakea has been at boiling point for a long time - the conditions, the lockdowns have been immense and they are stuck in their units for far too long.

"Some days, most days, they are lucky if they get one hour recreation. It is getting ridiculous."

A Department of Justice spokesperson said all other prisoners were safely secure but did not answer questions as to whether the prisoners had said why they were on the roof.