Following the U.S.-Republic of Korea military drills, North Korea fired four ballistic missiles into the sea off Japan's northwest on Monday in retaliation. The missiles flew on average 1,000 km and three of them landed in waters as close as 300 km (190 miles) from Japan's northwest coast, according to Japan's Ministry of Defence. Launched from the Tongchang-ri region, the type of the missiles are still unknown, although Republic of Korea's military officials said the missiles were unlikely to have been intercontinental ballistic missiles (ICBM).