WONSAN, NORTH KOREA — South Korea says the North has launched missiles into the sea, amid growing uncertainty about nuclear negotiations between Washington and Pyongyang. <br /><br />According to South Korea's Joint Chiefs of Staff, North Korea fired two unidentified projectiles from Wonsan on Thursday, at 5:34 and 5:57 a.m.<br /><br />Each flew at least 430 kilometers, at an altitude of 50 kilometers, before landing in the East Sea.<br /><br />Based on the flight range, the projectiles are believed to be the North Korean version of Russia's Iskander ballistic missile. They resembles the two short-range missiles Pyongyang fired in May.<br /><br />Vipin Narang, an associate professor of political science at MIT, told CNN the launch may be a response to the news that joint U.S.-South Korea military exercises will go ahead as planned next month, despite objections from North Korea.<br /><br />CNN reports that the launch came just days after North Korean state media released a photo of leader Kim Jong-un inspecting a submarine under construction, in what may be an attempt to showcase Pyongyang's military capabilities.