The worst mass shooting in New Zealand history claimed the lives of 49 innocent people in a massacre made more loathsome by the killer live-streaming his murders on Facebook.

Prime Minister Jacinda Ardern condemned today's attacks on two Muslim mosques in Christchurch as terrorism. Three persons are in custody, including an Australian in his late 20s who police say is the gunman who slaughtered helpless Muslim's at Friday prayers and wounded more than 20 others. The killer's name is probably Brenton Tarrant as can be seen from his online posts.

This man began his murderous rampage in which he shot his wounded victims in the head to ensure they were dead after publishing a "manifesto" in which he denounced immigrants, calling them "invaders," which is a language used by U.S. president Donald Trump.

The video footage from the killer's helmet camera was widely circulated on Facebook and other social media sites. The killer posted the footage live online as the attack unfolded.

The man burst into the mosque as worshippers were kneeling for prayers. The video showed him driving to one mosque, entering it and opening fire on everyone he came across.

It showed worshippers, possibly dead or wounded, huddled on the floor. A CNN journalist who viewed the 17 minute-long video feed said this man then exited the mosque and fired at people outside.

After getting another automatic rifle from his car, the gunman re-entered the mosque and began shooting the fallen victims in the head to ensure they were dead. He then came across a woman, who he shot, and shot again in the head as she whimpered in agony.

A man who said he was at the Al Noor mosque told media the gunman was white, blond and wearing a helmet and a bulletproof vest.

"He had a big gun ... he came and started shooting everyone in the mosque, everywhere," said the man. He said he and others escaped by breaking through a glass door.

Police said 41 people were killed at the Al Noor mosque and seven at a mosque in the Linwood neighborhood. One victim died in hospital. Children are among the victims.

The killer's online manifesto cited "white genocide", a term typically used by racist groups to refer to immigration and the growth of minority populations, as his motivation to murder.

The Facebook link directed users to the page of a user called brenton.tarrant.9. A Twitter account with the handle @brentontarrant showed images of a rifle and other military gear decorated with names and messages connected to white nationalism. These same weapons appeared in the live stream of the mosque attack on Friday.

"I blame these increasing terror attacks on the current Islamophobia post-9/11," said Pakistan's prime minister Imran Khan in a social media post. "1.3 billion Muslims have collectively been blamed for any act of terror."

Muslims account for just over 1 percent of New Zealand's population, said the government.