One person is in custody and multiple people were killed in shootings at at least two mosques in Christchurch, police said Friday. Officials believe others may be at large.

New Zealand Prime Minister Jacinda Ardern said at a news conference that she could not confirm the number of causalities and it was an “evolving situation” across multiple sites.

"It is clear that this is one of New Zealand’s darkest days," Ardern said. “Clearly, what has happened here is an extraordinary and unprecedented act of violence."

New Zealand Police Commissioner Mike Bush said in a statement that the situation was evolving "and we are working to confirm the facts, however, we can confirm there have been a number of fatalities” and that police were at a number of scenes. He asked all mosques across the nation to close to their doors.

Bush said police were dealing with "a very serious and tragic series of events" and "they involve an active shooter" and "multiple fatalities."

"We have one person in custody, but we are unsure if there are other people," Bush said in a video statement. Bush said in a written statement that "police believe there may be other offenders.

Officers responded to reports of shots fired in central Christchurch around 1:40 p.m. Friday local time (8:40 p.m. Thursday ET), police said in a statement. All schools in the city were placed on lockdown, and residents were urged to remain indoors.

Witness Len Peneha said he saw a man dressed in black enter the Masjid Al Noor mosque and then heard dozens of shots, followed by people running from the mosque in terror, the Associated Press reported.

Peneha said he went into the mosque to try and help: "I saw dead people everywhere,” he told the Associated Press.

Peneha, who said he has lived next door to the mosque for about five years, said the gunman ran out of the mosque, dropped what appeared to be a semi-automatic weapon in Peneha's driveway, and fled.

A member of the mosque told local media at the scene that he was in a side room where the imam was speaking and it was peaceful and quiet when "suddenly the shooting started." He did not see the shooter, but saw people running.

A witness told broadcaster One News that he had seen three people on the ground, bleeding outside the building, Reuters reported.

"Horrified to hear of Christchurch mosque shootings. There is never a justification for that sort of hatred," Amy Adams, a member of parliament from Christchurch, tweeted.

Christchurch City Council said in a statement that all council buildings were in complete lockdown, with no one allowed in or out.

Christchurch Mayor Lianne Dalziel in a local radio interview urged people to “please stay away from the central city until further notice."

She said she did not have details about the apparent shooting, but said “I never would have expected anything like this to happen in the city of Christchurch" or in New Zealand.

The Bangladesh cricket team was going to Friday prayers at the Masjid Al Noor mosque when the shooting occurred but all members were safe, a team coach told Reuters.

Although the Islamic faith requires praying five times a day, every day, Friday afternoon prayer services are highly revered because they are meant to be practiced as a community.

Many Muslims pray together at a mosque for the Friday afternoon prayer, referred to as Jumu’ah in Arabic.

The Quran contains specific verses referring to the Jumu’ah prayer as a day of assembly, a day for the Muslim community to come together in remembrance of their god, Allah.