Bangladesh, March 15 -- Multiple people were killed in mass shootings at two mosques full of worshippers attending Friday prayers on what the prime minister called "one of New Zealand's darkest days," as authorities detained four people and defused explosive devices in what appeared to be a carefully planned attack.

Prime Minister Jacinda Ardern said the events in Christchurch represented "an extraordinary and unprecedented act of violence" and acknowledged many of those affected may be migrants and refugees.

Police took three men and a woman into custody after the shootings, which shocked people across the nation of 5 million people.

Authorities have not elaborated on who they detained. But a man who claimed responsibility for the sho...