SYDNEY, March 16 (Xinhua) -- Australia's leaders have expressed shock and grief at Friday's deadly shootings in Christchurch, offering condolences to New Zealanders.

Prime Minister Scott Morrison confirmed that one of the perpetrators was born in Australia and described the incident as a "vicious and callous, right-wing extremist attack."

"I can confirm that the individual who was taken into custody I have been advised is an Australian-born citizen," Morrison said.

The man has been identified as 28-year-old Brenton Tarrant, who worked as a personal trainer in Grafton in the State of New South Wales (NSW) between 2009 and 2011, before leaving the country to travel in Asia and Europe.

The manager of the gym where Tarrant worked, Tracey Gray, told Australia's national broadcaster that at the time he did not seem like he had an interest in firearms.

"He was a very dedicated personal trainer," she said,

"He worked in our program that offered free training to kids in the community, and he was very passionate about that."

"I think something must have changed in him during the years he spent travelling overseas."

Representing Australia's Muslim community, Bilal Rauf from the Imams Council said that there was a sense of anger regarding the attack, as well as concern for the safety of those attending mosques.

"There is a sense of outrage, concern, and, yes, a concern about safety," he said.

"A concern about safety that someone could so readily walk into a place of worship where defenceless people were there together worshipping God with their children, with their wives, with their family members and they were mercilessly gunned down."

Police commissioner of the state where Tarrant lived has condemned "right-wing extremism" and is considering assigning extra resources to help combat it.

"We have arrested right-wing extremists in this state. We have criminal orders against right-wing extremists. We take it seriously," NSW police commissioner Michael Fuller said.

"We know that in some western countries it is an emerging risk and we're certainly looking at it closely."

Opposition leader Bill Shorten has extended his sympathies to all those affected in a speech to the Islamic Council in the State of Victoria.

"It was an Australian who did this, but this is not an Australian who represents Australia," he said.

He said that the majority of Australians felt "impotent, outraged, disgusted, ashamed."

"There are...millions of Australians who feel solidarity with you today."

"Now is the time to repudiate once and for all not just the violence, but the circumstances, the hate speech, that fuels the violence."