From the Washington Post's blogPost:
A rumor that an explosion accrued at North Korea’s Yongbyon nuclear facility set off a brief panic Friday in the South Korean stock market, illustrating one of the ways in which Seoul is vulnerable to its neighbor.
South Korean government officials found zero evidence that an explosion had actually occurred, and a visiting U.S. diplomat in Tokyo said he’d heard nothing to suggest the rumor was true. Radiation-monitoring devices in the region showed no unusual activity.
Still, the rumor reflected concerns — often discussed among nuclear experts — about the unregulated nuclear activity in the North; the possibility that North Korean technicians would struggle to contain an accident if one occurred; and the widely held belief that the government in Pyongyang would neglect to warn the region about spreading radiation.
In this case, the rumor caused the South Korean stock market to dip and the won to weaken against the dollar. South Korea’s financial regulator asked police to investigate the source of the rumor, and said he believed it may have been spread by someone who wanted to profit by manipulating the market.
According to South Korea’s Yonhap news agency, the rumor cited information from an unidentified Japanese intelligence source stationed in North Korea. Yonhap said that the rumor quickly spread among securities firms and on the Internet, starting shortly after 2 p.m. But it gave no specifics about how or where the rumor originated.
The KOSPI Composite Index plummeted for almost 15 minutes. But it recovered those rumor-fueled losses before the end of the trading day....MORE
