Two days after ships from the rival Koreas clashed in disputed waters, the North is warning the South it was pay “an expensive price” for the incident.Pyongyang’s official newspaper dubbed the South “warmongers who like to play with fire.” It said the skirmish was a conspiracy by Seoul’s military to thwart a current thaw in tensions. Despite the strained atmosphere, the South offered reassurances about regional security, saying there had been no unusual activity in a common industrial zone within North Korea where South Korean citizens live. Navies from the two sides exchanged gunfire for the first time in seven years on Tuesday, each blaming the other for violating a sea border. A sailor from Kim Jong-il’s North Korean navy was reportedly killed in the clash. Despite the escalation in tensions, American Secretary of State Hillary Clinton says Washington still plans to send a special envoy to North Korea.