Seoul, South Korea, June 25, 2010, SPA -- North Korea banned boats off its west coast, a South Korean official said today, in a possible indication the country may hold an artillery drill or even conduct missile tests, AP reported. The official with the Joint Chiefs of Staff said that South Korea is closely monitoring the North's military, though he added that no unusual movements had been detected. He declined to give further details and asked not to be named as the matter involves military intelligence. The poorly marked sea frontier _ drawn by the American-led U.N. Command at the end of the 1950-53 Korean War _ is a constant source of tension between the divided Koreas. Their navies engaged in bloody battles in the area in 1999, 2002 and last November. In Washington, the State Department noted that North Korea had previously made such announcement ahead of missile launches. Spokesman P.J. Crowley said a missile launch would be counterproductive and inflame already heightened tensions in the region. «This is a time for North Korea to take steps to reduce tenstions in the region,» Crowley told reporters. «Declaring no sail zones which, given past North Korean behaviour, raises the potential that they might use this as a notification for a missile launch.» «That would certainly be a step in the wrong direction and we would discourage North Korea from taking that step,» Crowley said. South Korea's Yonhap news agency cited an unidentified government source as saying the no-sail zone was set from June 19-27 north of the port of Nampo, 50 miles (80 kilometers) from the disputed inter-Korean sea border. The North has set similar restrictions before past missile tests or firing drills. In January, North Korea designated no-sail zones and fired artillery as part of an annual drill near the western sea border. The North's latest move came amid heightened tensions over the deadly sinking of a South Korean warship near the western sea border in March that killed 46 South Korean sailors. --SPA 21:45 LOCAL TIME 18:45 GMT www.spa.gov.sa/796029