North Korea has fired three short-range missiles off its west coast, Yonhap news agency reported Saturday.The South Korean agency, quoting a government source, said the missiles were fired on Friday into the Yellow Sea off Jeungsan County, some 40 kilometres (25 miles) west of Pyongyang.The testing was part of a military training exercise involving Russian-designed Styx ship-to-ship missiles with a range of 46 kilometres, the report said."The missile launch, like the test-firing conducted on March 28, is part of normal military training aimed at testing the performance of the missiles and improving operational readiness," the source was quoted in the report saying.A South Korean defence ministry spokesman refused to comment.