South Korea and the U.S. have detected signs that North Korean submarines that left their bases are returning, following an agreement between the two Koreas.
 
A military official in Seoul said Tuesday that some of around 50 North Korean submarines which vanished since Friday have been detected making their way back to their bases.
 
The official said that the submarines are believed to have remained in the North’s inland sea.
 
The South Korean Navy had strengthened its antisubmarine patrol activities, after some 50, or roughly 70 percent, of the North’s submarines, left their bases in the East Sea and the Yellow Sea on Friday.