A U.S. ban on its citizens travelling to North Korea has come into effect, at a time of heightened tensions over North Korean missile launches. The new rule was announced after U.S. student Otto Warmbier died after being released from prison in North Korea. The State Department said it was necessary "due to the serious and mounting risk" of detention.

Chinese hackers in March broke into the computer networks of the United States government agency that houses the personal information of all federal employees, according to senior American officials. They appeared to be targeting the files on tens of thousands of employees who have applied for top-secret security clearances. The hackers gained access to some of the databases of the Office of Personnel Management before the federal authorities detected the threat and blocked them from the network, according to the officials.