More missiles launched from North Korea's coast as tensions continue to escalate.
South Korea said its neighbour had fired two short-range missiles into the sea on Monday, making six launches in three days.
The North said military exercises were the legitimate right of any country and that it was coping with what it called "mounting war measures from the U.S. and South Korea".
Pyongyang has condemned joint U.S.-South Korean military drills, repeatedly threatening nuclear attacks against both countries.
The United Nations Security Council imposed tougher sanctions against North Korea following its third nuclear test in February.
Missile launches by the North are not uncommon, but have raised concerns about regional security amid threats from Pyongyang.
