Seoul (AFP) – North Korea fired more than 20 missiles Wednesday, including one that landed close to South Korea’s waters in what President Yoon Suk-yeol said was “effectively a territorial invasion”. It also fired an artillery barrage into a maritime “buffer zone” that experts said was part of an “aggressive and threatening” response by Pyongyang to large-scale joint air drills the United States and South Korea are conducting. One short-range ballistic missile crossed the Northern Limit Line, the de facto maritime border, prompting a rare warning for residents on the island of Ulleungdo to see…