North Korea ratchets up tension on Seoul

A US Air Force F-22 stealth fighter jet takes off from the Osan US Air Base in Pyeongtaek on April 3

A US Air Force F-22 stealth fighter jet takes off from the Osan US Air Base in Pyeongtaek on April 3. Yon Hap/AFP

North Korea have blocked access to a key joint industrial zone with South Korea, a sharp escalation in a military crisis that Washington blamed on Pyongyang’s “reckless” behaviour. The US has positioned a warship off the Korean coast as a shield against ballistic missile attack, and also deployed radar-evading F-22 Raptors on Sunday to take part in the annual joint military drills it carries out with South Korea.