The United Nations chief has voiced hope that North Korea will abandon its missile tests, after the Stalinist state fired three short-range missiles into the sea on Saturday.
Speaking in Russia on Sunday, UN Secretary General Ban Ki-moon called on Pyongyang to refrain from future launches and return to stalled nuclear talks with world powers.
Mr. Ban is in the Black Sea resort town of Sochi to meet with Russian President Vladimir Putin for talks on Syria.
South Korea said Saturday that North Korea had fired two short-range missiles into the East Sea -- also known as the Sea of Japan in the morning, followed by another in the afternoon.
A South Korean defense ministry spokesman said the North's intent was not clear. He said South Korea's military was watching for any additional launches and "possible provocation."
The development comes during a period of tentative diplomacy aimed at easing tensions. Earlier this year, Pyongyang threatened nuclear strikes on South Korea and the U.S. in light of annual U.S.-South Korean military drills and U.N. sanctions imposed on the North after its third nuclear test in February.
About two months ago, North Korea fired off two short-range missiles into the sea off its east coast. Pyongyang routinely conducts such exercises in an effort to improve its arsenal.