SEOUL, South Korea — A rocket launched by North Korea to deploy the country’s second spy satellite exploded shortly after liftoff Monday, state media reported, in a setback for leader Kim Jong Un’s hopes to field satellites to monitor the U.S. and South Korea.

Monday’s failed launch came hours after leaders of South Korea, China and Japan met in Seoul in their first trilateral meeting in more than four years. It’s highly unusual for North Korea to take provocative action when…