A North Korean border guard shot and killed three Chinese citizens and wounded a fourth on the countries' border last week, China said Tuesday after lodging a formal diplomatic protest. The guard shot the four residents of the northeastern border town of Dandong last Friday, apparently on suspicion they were crossing the border for illegal trade, Foreign Ministry spokesman Qin Gang said. "On the morning of June 4, some residents of Dandong, in Liaoning province, were shot by a DPRK border guard on suspicion of crossing the border for trade activities, leaving three dead and one injured," he said at a regularly scheduled press conference. He used the acronym for North Korea's formal name, the Democratic People's Republic of Korea. "China attaches great importance to that and has immediately raised a solemn representation with the DPRK. Now the case is under investigation," he said.