Police Commissioner Mike Bush has urged people not to travel to mosques "anywhere in New Zealand" tonight.

As the country reels in the horror of today's mass shooting in Christchurch – which has lead to multiple deaths and injuries – Bush called for people to stay away from mosques, which were expected to be packed today for Friday prayers.

"I want to ask anyone who was thinking of going to a mosque anywhere in New Zealand not to go, to close your doors until you hear from us again," Bush said.

Bush confirmed the shootings had resulted in "multiple fatalities".

He said there was one person in custody "but we are unsure if there are other people".

The multiple fatalities were at two locations: a mosque at Deans Ave and one at Linwood Ave.

"Again we are unsure if there are any other locations outside of that area," he said.

"We have mobilised every police resource in the Canterbury location to respond to this and we are also in the process of mobilising every national police resource to keep people safe."

Moath Owaidah, of the New Zealand Islamic Union Trust, said a large group were exiting their Friday prayer session at Masjid Al Maktoum mosque near Auckland Airport when they started getting calls about the shootings.

"We started getting calls from the Islamic community. The reaction of some of the people there, they were really shocked and very nervous about what happened, because it's something you don't expect here in New Zealand," Owaidah said.

"A family that we know, their father was at the prayers, and they've been trying to get in contact with him and so far they haven't been able to, so we're still trying to get more information on that. People are worried."