Police have yet to provide the number of casualties, but the incident could potentially be the deadliest shooting in the country.
Here's what world influencers had to say:
New Zealand Catholic Bishops Conference
"Dear Members of the Muslim community in Aotearoa New Zealand, We hold you in prayer as we hear the terrible news of violence against Muslims at mosques in Christchurch," the New Zealand Catholic Bishops Conference said.
"We wish you to be aware of our solidarity with you in the face of such violence. Peace, Salaam."
Apple CEO Tim Cook
"Devastated by the reports out of New Zealand," Cook said on Twitter. "The community in Christchurch is in our hearts, as are all affected by this horrific attack."
Cook ended the tweet with a quote from civil rights leader Martin Luther King Jr.: "I have decided to stick with love. Hate is too great a burden to bear."
Democratic Rep. Alexandria Ocasio-Cortez of New York
Ocasio-Cortez listed the names of cities where previous mass shootings occurred in the US.
"At [first] I thought of saying, 'Imagine being told your house of faith isn't safe anymore,' Ocasio-Cortez said on Twitter. "But I couldn't say 'imagine.' Because of Charleston. Pittsburgh. Sutherland Springs."
"What good are your thoughts & prayers when they don't even keep the pews safe," Ocasio-Cortez said.
Ocasio-Cortez qualified her remark, adding that her phrase was in reference to the NRA's "phrase used to deflect conversation away from policy change during tragedies."
"Friends, Morning (Friday) is Jummah, the weekly day of worship for our community of Muslim friends and loved ones," the lawmaker added. "Be there for them. Check in. Perhaps extend a kind gesture at your local mosque. There is so much fear and hate. We must negate it with active, courageous love."
US ambassador to New Zealand Scott Brown
"Were heartbroken over the events in Christchurch today," Brown said in a brief statement, adding the Mori phrase for "stay strong." "We stand with our Kiwi friends and neighbors and our prayers are with you. Kia kaha."
New Zealand rugby team All Blacks
"Christchurch, we stand with you during this time," the rugby team said. "Our thoughts and sympathies are with everyone affected by today's tragedy. Stay strong. Kia Kaha."
New Zealand Prime Minister Jacinda Ardern
TV New Zealand / TV New Zealand / AFP
"What has happened in Christchurch is an extraordinary act of unprecedented violence," the prime minister said. "It has no place in New Zealand."
"Many of those affected will be members of our migrant communities New Zealand is their home they are us," she continued. "The person who has committed this violent act has no place here."