Ms. Ardern said none of those detained had been on security watch lists.

Mr. Bush had earlier urged people not to go to mosques anywhere in New Zealand on Friday. He also urged mosques nationally to “close your doors until you hear from us again.”

Handcuffed suspect appears in court

In a Christchurch courtroom hearing closed to the public for security reasons, police officers in bulletproof vests brought in the suspect, Brenton Harrison Tarrant. The police said he had been charged with one count of murder but would face additional charges. Mr. Tarrant, 28, short with thinning brown hair, handcuffed and wearing white prison clothing, looked around the courtroom but said nothing as District Court Judge Paul Kellar ordered him held for a further hearing on April 5.

Regional officials have said Mr. Tarrant is an Australian citizen. Court papers listed his New Zealand address as Dunedin City, which is about 280 miles south of Christchurch.

Richard Peters, his court-appointed lawyer, said Mr. Tarrant had indicated he might represent himself in the prosecution. Asked how Mr. Tarrant had reacted to what he is facing, Mr. Peters said, “He seemed to be quite aware of where he is and what he’s doing.”

At the same time the charging document for Mr. Tarrant was handed out to reporters, a second court filing was distributed that said Daniel John Burrough, 18, of Christchurch, had been charged with “intent to excite hostility or ill-will.” Court officials would not elaborate on how the two cases were related.

In addition to Mr. Tarrant, three other people were arrested in connection with the attacks, although one was apparently released. Few details have been offered about them.

A range of nationalities among the dead and injured

Families are mourning loved ones, and the city of Christchurch is preparing to bury its dead. As news trickles out about the victims of the massacre, their nationalities are beginning to emerge.

Though officials have not released the names of those killed, a list of those missing has been published by the New Zealand Red Cross on its website. It includes people from Afghanistan, Bangladesh, India, Jordan, Pakistan and Saudi Arabia.

At least three people from Bangladesh were killed, and another two from Jordan, according to local news reports. Five people from Pakistan are missing, and several others were injured, officials in Pakistan confirmed. Other foreign ministries around the world said their citizens were caught up in the attack, including three people from Turkey.

Video shows part of the shooting

A 17-minute video posted to Facebook shows part of the attack.

The clip, which appeared to have been taken from a helmet camera worn by the gunman, begins behind the wheel of a car. A man, whose face can occasionally be seen in the rearview mirror, drives through the streets of Christchurch before pulling up in front of Al Noor Mosque, beside the sprawling Hagley Park.

[Read more here about the video, manifesto and social media posts.]