SYDNEY (Reuters) - Violence has flared at an Australian asylum-seeker detention center in Papua New Guinea (PNG), and shots were fired when local people tried to break into the center after an argument got out of hand, media and a rights group reported on Saturday.

There were no reports of serious injuries at the center on Manus island but the trouble is likely to add to pressure on Australia from rights groups and the United Nations to close it and another center in Nauru, criticized over poor conditions.

Australia’s ABC broadcaster said a large number of PNG men tried to break into the detention facility on Friday evening and police fired shots to disperse them.

The men came back with guns and fired up to 100 rounds into the facility’s accommodation wing, ABC reported.

Australia’s Department of Immigration and Border Protection confirmed in a statement that there had been trouble.

“There was an incident at the Manus RPC overnight involving residents and PNG military personnel,” the department said, referring to the so-called regional processing center.

“PNG military personnel discharged a weapon into the air during the incident. The incident was quickly resolved.”

One inmate was reportedly hit in the head by a rock thrown over the fence and was getting treatment, a department spokeswoman said.

She declined to comment on a report two guards had been injured or that shots were fired into the complex. She referred questions to PNG authorities.

PNG officials were not immediately available for comment.

Images posted on social media appeared to show bullet holes in the walls of the camp accommodation wing.

The incident was believed to have been sparked by an altercation between asylum seekers and a PNG resident, the rights group Amnesty International said.

Australia has a strict policy of not allowing anyone who tries to reach the country by boat to settle there, instead detaining them in the Pacific camps, where asylum claims processing can take years. Even if people are found to be genuine refugees, they are barred from Australia.

The policy has drawn criticism from the United Nations and rights organizations amid a global debate on how to manage people displaced by conflict.

Many of the people trying to reach Australia have been from the Middle East and Afghanistan.

Attempts in recent years to resettle some of them in Cambodia and Malaysia collapsed.

The PNG Supreme Court last year ruled that the detention of asylum seekers on Manus breached the constitution and ordered that the camp be closed.