At least 49 people were killed in shooting rampages at two Christchurch mosques on Friday, police said, with New Zealand Prime Minister Jacinda Ardern declaring the episode a "terrorist attack."

A total of 48 people, including young children, were being treated for gunshot wounds following the afternoon mass shootings at the mosques, which were packed with worshippers during Friday prayers.

(New Zealand Prime Minister Jacinda Ardern speaks to the media on March 16, 2019 in Wellington.)[Getty/Kyodo]

Police said three people are in custody for the attacks in the largest city of the country's South Island, with one of them, a man in his late 20s, being charged with murder. He is scheduled to appear before a local court on Saturday. The police have not identified any of the suspects.

Ardern, at a press conference, described the attackers as having "extremist views that have absolutely no place in New Zealand, and in fact have no place in the world." She raised the country's national security alert to high.

Australian Prime Minister Scott Morrison, meanwhile, said one of those in custody had been confirmed as an Australian-born citizen and Australian authorities were assisting in the investigation.

Earlier at a televised news conference, Police Commissioner Mike Bush said police discovered several improvised explosive devices strapped to vehicles that were subsequently disarmed.

Ardern said the explosive devices showed the attack was well planned.

(Police Commissioner Mike Bush speaks to media during a press conference at Royal Society Te Aparangi.)[Getty/Kyodo]

The first shooting occurred at around 1:45 p.m. local time at the Al Noor mosque on Deans Avenue in central Christchurch. Also attacked was the Linwood Islamic Center on Linwood Avenue about 5 kilometers to the east.

A total of 41 people were fatally shot at the Masjid Al Noor mosque and seven at the Linwood mosque. One person died of injuries in hospital.

The Malaysian Foreign Ministry confirmed that two Malaysian nationals were injured in the shootings.

According to the Indonesian Embassy in Wellington, six Indonesians were praying at the Al Noor mosque, of whom five were confirmed safe but one is still unaccounted for. There were two Indonesians -- a father and a son -- at the Linwood mosque and both were injured. The father is in critical condition and the son is stable.

The gunman had earlier posted a "manifesto" in which he described himself as an "ordinary white man" and denounced immigrants as "invaders," according to media reports.

Police have urged people not to view or share an online video apparently streamed live of one of the attacks.

The 17-minute video, filmed with a helmet camera, reportedly shows the entire incident, as well as the gunman's cache of weapons and ammunition.

(Locals lay flowers in tribute to those killed and injured at Deans Avenue near the Al Noor Mosque on March 16, 2019 in Christchurch.)[Getty/Kyodo]

"Police are aware there is extremely distressing footage relating to the incident in Christchurch circulating online," the police said on Twitter.

Following the incident, schools throughout Christchurch were placed on lockdown. Police later confirmed the lockdown had been lifted but urged locals to remain indoors.

"Police are still treating this incident as ongoing and Christchurch residents are strongly urged to stay indoors and keep safe," Bush said.

Bush asked anyone considering going to a mosque "anywhere in New Zealand today" to refrain and to close the doors "until you hear from us again."