Singapore authorities said on Monday they had arrested three teenagers over separate plots to carry out shooting, stabbing and bomb attacks, warning of the threat of “youth radicalisation” in the security-conscious city state. The three boys, detained between April and June, had been “self-radicalised” online, adopting violent extremist ideologies, the Internal Security Department (ISD) said. They are held under the Internal Security Act, which allows for detention without trial. One of them, a...