Australian Prime Minister Scott Morrison has expressed his "heartfelt sympathies" for New Zealand following the attacks in Christchurch.

The terrorist attack in Christchurch has left 49 dead and 48 injured on Friday, New Zealand police said.

"We grieve, we are shocked, we are appalled, we are outraged, and we stand here and condemn absolutely the attack that occurred today by an extremist, right-wing, violent terrorist," Morrison told reporters on Friday evening.

"This attack reminds us of the evil that his ever present and would seek to strike out at any time."

"I particularly want to express my sincere prayers and thoughts for those New Zealanders, indeed Australians of Islamic faith today, who have been the subject of this callous right-wing extremist attack."

New Zealand Police Minister Mike Bush confirmed that three men and one woman were in police custody in relation to the multiple shootings at two separate mosques in central Christchurch.

Bush said he was aware that the footage of the Al Noor Mosque shooting was on social media and police were doing everything they could to get it removed.

"I found the advice of the New Zealand police force to be particularly wise. They have said, and I agree, and do not allow this evil into our lives. Do not share the footage. Do not watch the footage," Bill Shorten, leader of the opposition Australian Labor Party, told reporters.