Two Canadian diplomats working for the United Nations in Niger have been missing since Sunday night, United Nations officials said Monday. A car that had been carrying the diplomats — Robert Fowler, the United Nations’ special envoy to Niger, and Louis Guay, his assistant — and that bore lettering identifying it as a United Nations vehicle was found abandoned about 30 miles northeast of Niamey, the capital. The driver was also missing. Mr. Fowler served previously as Canada’s ambassador to the...