By Frances Mao in Singapore & Jean Mackenzie in SeoulBBC NewsNorth and South Korea have both fired missiles landing in waters off each other's coasts for the first time.Seoul retaliated on Wednesday three hours after Pyongyang launched a missile that landed less than 60km (37mi) off the South's city of Sokcho.The South's military said this was an "unacceptable" breach of its territory.It fired three air-to-ground missiles in response, which officials said landed a similar distance past the Northern Limit Line (NLL).The demarcation line marks the rough midway-point in the sea between...…By Frances Mao in Singapore & Jean Mackenzie in SeoulBBC NewsNorth and South Korea have both fired missiles landing in waters off each other's coasts for the first time.Seoul retaliated on Wednesday three hours after Pyongyang launched a missile that landed less than 60km (37mi) off the South's city of Sokcho.The South's military said this was an "unacceptable" breach of its territory.It fired three air-to-ground missiles in response, which officials said landed a similar distance past the Northern Limit Line (NLL).The demarcation line marks the rough midway-point in the sea between...WW…