The Nauruan government is backtracking on its commitment to process 600 refugee claims "within the next week", saying about 400 will be completed by Sunday but others may not be concluded for weeks.

The Pacific nation issued a statement on Monday declaring it would quickly finalise the claims of all remaining asylum seekers.

The country also announced curfews would be lifted, making the Australian Government-funded facility an "open centre".

But deputy director of Nauru's Department of Justice and Border Control, Shyla Vohra, said the processing timeline does not apply to people outside Nauru or their families.

"There are some people who are overseas for medical transfers," Ms Vohra told ABC's Radio National.

"We're also not going to be handing down the determinations for family members for anyone who is overseas for a medical transfer, so that we can do family determinations together."

Ms Vohra said about 20 additional staff had been recruited to handle the workload, and the team had identified some applications requiring more work.

"There are going to be some cases that can't be finalised quickly for whatever reason, or [where people] need to be re-interviewed, or where we consider we need further information or further research to be done.

"The remaining cases where we need to do further research and re-interviews we're hoping to get done in the next few weeks; it depends on the complexity of the case really."

The one-week timeframe also will not apply to people who have raised additional claims after their interview.

Ms Vohra said about 75 per cent of asylum seekers processed have been recognised as refugees, but most whose claims have been rejected are appealing.

Greens urge Nauru to thoroughly assess all cases

Greens immigration spokeswoman Sarah Hanson-Young said the country had made misleading claims all week.

"What we've seen from the Nauru government all week is spin, what we've seen from the Australian Government is more hiding behind the spin of the Nauruan government," Senator Hanson-Young said.

"It seemed quite surprising that the Nauru government could go from processing virtually nobody to all of a sudden getting 600 claims done by the end of the week."

Senator Hanson-Young said the process should be fair and thorough, and added that people might need help with their claims.

"A proper process that ensures their claims are assessed fully [and] that they have a fair process to appeal," she said.

"This can't just be a tick and flick; this has to ensure that people at the end of the day are given protection."

The ABC has contacted the Federal Government for comment.

Monday's decision to process all remaining asylum seekers came just days before a legal challenge examining the Australian Government's role in the centre's operation.

However Immigration Minister Peter Dutton said the announcement from Nauru had nothing to do with the court case.

Over the past two days the full bench of the High Court heard arguments that it was illegal for the Government to operate and pay for offshore detention in a third country.

If the court agrees, the whole offshore detention regime could be deemed invalid.