A British teenager on Monday pleaded guilty to charges of murdering three young girls in a knife attack in northern England in July, a crime that horrified the nation and was followed by days of nationwide rioting.

Home Secretary Yvette Cooper said agencies "failed to identify the terrible risk and danger to others" that Axel Rudakubana posed - and answers are needed about why.

A British teenager unexpectedly pleaded guilty on Monday to murdering three young girls at a Taylor Swift-themed dance event last July, while the government said it would hold an inquiry into the atrocity which was followed by nationwide rioting.