North Korea test-fired two short-range missiles from its eastern coast Thursday.
South Korean media reported the missiles that were launched were ground-to-ship missiles.
"It's not a good sign because they are demonstrating their military power," South Korea's Foreign Minister Yu Myung-hwan told The Associated Press.
North Korea's action comes despite the new U.N. sanctions that were imposed to punish the country for its recent nuclear tests.
"We had expected that they will fire short-range missiles at any time," Myung-hwan added.
North Korea had earlier called for a no-sail zone in waters off its east coast through July 10 for military drills, which was viewed as a pathway to the missile tests.
The missile tests also follow news that a suspicious North Korean ship changed course earlier this week.
The ship had been under U.S. surveillance following reports that North Korea would test-fire a long-range missile toward Hawaii as early as July 4.