Pyongyang's sabre rattling reaches new peak as line to Seoul allowing cross-border travel by citizens is closedNorth Korea has cut off a key military hotline with South Korea that allows cross-border travel to a jointly run industrial complex in the North, a move that ratchets up tension and puts the last major symbol of inter-Korean co-operation in jeopardy.North Korea recently cut a Red Cross hotline with South Korea and another with the US-led UN command at the border between the Koreas, but there is still a hotline linking aviation authorities in the North and South.North Korea's chief delegate to inter-Korean military made the announcement on Wednesday, in a statement sent to his South Korean counterpart.