Asylum seekers at the Manus Island detention centre have accused guards of deliberately building tensions by escalating their presence and searches ahead of Wednesday's High Court decision.

Behnam Satah, an eye-witness to the killing of Reza Barati two years ago, also claims some guards who took part in the violence against detainees in February 2014 have returned to the centre.

Mr Satah, who is now receiving torture and trauma counselling, said he had reported the return of one of those who supervised guards who beat detainees during the 2014 riots.

"I asked him: 'What are you doing here after all this time?' And he said: 'It's our job'."

Mr Satah said there were no plans for peaceful protests to coincide with Wednesday's judgment on a challenge to the lawfulness of the Australian Government's role in offshore detention on Nauru.

But he said the Emergency Response Team had stepped up its presence to intimidate detainees and that mobile phones were being confiscated.

"They want to build tension. We told them: 'We know that you have power. When you know we are weak, why you want to show us your power?' We are not violent people, we are not troublemakers. Our problem is not with you'.

"The only thing we want is freedom and 31 months we have been stuck here and no one tells us what is going to happen to us, what is our future."

Detainees are also in a heightened state of anxiousness because this month will see the anniversary of the 2014 riots, when scores of asylum seekers were injured and Mr Barati was killed, and the jailing of asylum seekers who took part in a peaceful protest last year.

"Australia made me hate the month I was born. It's very hard. Everyone is going crazy here. Everyone is depressed."

Mr Satah said he had no hesitation in putting his claims on the public record, saying: "I have nothing to lose. I receive threats every day."

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