Police used pepper spray on Australia detention protesters

Serco staff called in the Australian federal police after guards were apparently overwhelmed by about 100 asylum-seekers from war-torn countries such as Iraq, Afghanistan and Somalia.

Riot police eventually gained control of the situation by unleashing "less than lethal munitions" including pepper spray, a bean-bag round and "distraction devices" against protesters - some of whom had reportedly been armed with improvised weapons.

One Serco employee suffered a light wound, according to an immigration spokeswoman, who said that no refugees had sustained injuries.

Refugee Action Collective activist Ian Rintoul alleged that the protest had been provoked by the actions of Serco staff.

"My information is the involvement of so many people in the protest was in response to Serco's heavy-handedness when it tried to remove at least one person from the compound," Mr Rintoul said.

"Those people took the protest action to stop him being taken to isolation."

Greens senator Sarah Hanson-Young, who visited the facility this week as part of a parliamentary probe, repeated her party's call for limits on how long asylum-seekers can spend in detention and an overhaul of mandatory detention.

Ms Hanson-Young noted that Christmas Island detainees "are desperate because they are in long-term and indefinite detention.

"It's a jail where they are locked up, except unlike criminals who know when their sentences are ending, these people have no idea."