Washington is concerned about the recent detention of a fourth U.S. citizen in North Korea and is working with the Swedish Embassy in Pyongyang to resolve the issue, White House Spokesperson Sean Spicer said at a regular press briefing in the U.S. capital on Monday.

"Obviously this is concerning, we’re well aware of it and we’re going to work through the embassy of Sweden, that has an embassy in North Korea, through our State Department to seek release of the individuals there," Spicer told assembled reporters.