North Korea fired four short-range missiles over the sea off its east coast on Thursday, a media official at South Korea's Defence Ministry said, while providing no information on the purpose of the firing.
North Korea fired the missiles at 5:42 p.m. (0842 GMT) from a mountain site just north of the border with South Korea, the official said.
Launches by the North of short-range missiles are not uncommon as part of military exercises.
The firing came days after the beginning of annual joint U.S. and South Korean military exercises which the North routinely denounces as preparation for war.
The North was angered this month when a nuclear-capable U.S. B-52 bomber made a sortie over South Korea, though the flight did not trigger a sharp escalation of military tension.
The South's Yonhap News Agency said the missiles fired on Thursday were believed to have a range of about 200 km (125 miles), which means they could not reach Japan.