The USS Blue Ridge (LCC-19), the flagship of the US Navy's 7th Fleet, docks at a naval base in Busan, South Korea, 25 September 2025, to load military supplies and allow the crew to rest. EPA/YONHAP SOUTH KOREA OUT 
The incursion early on Friday also involved South Korean military transmitting verbal warnings and the operation followed standard protocol, the South's Joint Chiefs of Staff said in a statement.
The waters around the so-called Northern Limit Line border, which was drawn up after the 1950-53 Korean War, have been the scene of deadly naval clashes in the past. North Korea does not recognise the line as the border.
(Reporting by Jack Kim; Editing by Jacqueline Wong and Michael Perry)