Prime Minister Jacinda Ardern has announced a Royal Commission of Inquiry will be held into the Christchurch mosques terror attack.

She says people are asking how the attack, in which 50 people died and dozens more injured, was able to take place, including how the alleged gunman obtained the weapons, the role of social media and the role of agencies.

Ardern says she also has questions.

The inquiry will focus on whether security agencies were focused the right way and whether there were any clues that were missed.

And an Al Noor Mosque shooting survivor is looking for the woman who saved her and her baby's life, hoping she can thank her.

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