(CNN) -- Police in the New Zealand city of Christchurch said that there are "multiple fatalities" after active shooters opened fire in two mosques in the city center.
Police Commissioner Mike Bush said that one person is in custody but police are unsure if there are any other suspects.
"As far as we know (the shootings occurred) at two locations, a mosque at Deans Avenue, and another mosque at Linwood Avenue," Bush said. "We are unsure if there are any other locations outside of that area that are under threat."
Bush said they were "dealing with a very serious and tragic series of events in the Christchurch Canterbury area" and warned people to stay off the streets. He asked "anyone who was thinking of going to a mosque anywhere in New Zealand today not to go. To close your doors until you hear from us again," he said.
New Zealand's Prime Minister Jacinda Ardern held a press conference into the shooting at two mosques in Christchurch, describing it as "one of New Zealand's darkest days."
"What has happened here is an extraordinary and unprecedented act of violence," she said.
Ardern said the attacker has "no place in New Zealand."
"For now my thoughts and I'm sure the thoughts of all New Zealanders are with those who have been affected their families," she said.
Police said they were in the process of mobilizing every national police resource to respond to the incident.
Parts of Christchurch were put on lockdown as armed police were deployed after receiving reports of shots fired in the city center at 1:40 p.m. Friday local time.
Speaking to CNN, witness Mohan Ibn Ibrahim said he was inside the mosque when the shooting began and that he heard the gunman "continuously shooting for ten to 15 minutes."
"I was in the mosque. It's a big mosque and there were more than 200 people inside. The gunmen came from the backside. Gunshots went on for a long time. We had to jump the wall to escape. I saw lots of broken glass and bricks on the backside of the mosque," he said.
"I came to the street I saw one person got shot on his chest," he said, adding that the ambulance and police then arrived on the scene.
He said that he had a friend in another mosque in the area had told him a gunman had opened fire there as well and five people were dead.
"I could not contact two of my friends who are in the mosque as well," he said.
A spokesperson at Christchurch Hospital told CNN that "multiple" casualties had been sent there, but did not confirm the number.
Police are aware of a video shared online and not verified by CNN that purports to show a gunman walking into an unnamed mosque and opening fire.
Witness Mohammed Nazir told TVNZ that he "heard the big sound, the gun" at about 1.45 p.m.
"The second shot, I run, lots of people were sitting on the floor," he said. "The gun was (at the) front door, I run behind the mosque and I was sitting behind... and I called the police."
According to TVNZ, Nazir saw multiple deaths and injuries, including three women on the ground outside the mosque.
Canterbury Police NZ tweeted: "We have a critical incident in Deans Ave Christchurch. Please avoid the area. We will give more in the near future."
Bush said in a statement that "all Christchurch schools have been placed into lockdown."
"Police urge anyone in central Christchurch to stay off the streets and report any suspicious behavior immediately to 111," he added.
Christchurch City Council tweeted that it was locking down a "number of central city buildings, including the Civic Offices and Central Library."
A video posted on Twitter showed Bangladesh's cricket team walking away from the mosque. Speaking to CNN, the team's coach said their bus had pulled up at the mosque when shooting happened.
Christchurch is a coastal city of 404,500 residents. It is the second most-populous city in New Zealand behind Auckland and Wellington. It has an agricultural economy.
In 2010 and 2011 the city suffered a series of devastating earthquakes, with the most destructive at 6.3 magnitude, which killed nearly 200 people and destroyed thousands of buildings.
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