Several people, including an Australian national have taken into police custody, and one person has been charged with murder. It is unclear how many people were involved in the attacks.
New Zealand police said that several improvised explosive devices (IEDs) were found in a car near the Al Noor mosque. These were disabled before they could be detonated.
Other prominent Catholic figures expressed condolences to those affected by the attack.
"I share [Pope Francis'] deep sadness and grief over the deadly violence in Christchurch. No one should have to fear something like this, perpetrated as they worship. We cannot tolerate hatred of or prejudice against any of the Lord's children," said New York archbishop Cardinal Timothy Dolan in a message posted to Twitter.
Cardinal Vincent Nichols of Westminster expressed similar sentiment.
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"The news of the massacre in the New Zealand mosques is deeply shocking and has caused us all great pain. We pray for the many victims, for the wounded and for the whole community, which has been severely affected by this act of terrorism," said Nichols.
"May God free us from these tragedies and sustain the efforts of all those who work for peace, harmony and coexistence."