North Korea fired four ballistic missiles early on Monday, three of which landed in Japan's exclusive economic zone, Japanese Prime Minister Shinzo Abe said, the latest in a series of provocative tests by the reclusive state.
"Multiple ballistic missiles" were launched from the Tongchang-ri region near the North's border with China and flew about 1,000 km (620 miles), South Korean military officials said, without providing the number of missiles.
"South Korea and the United States are conducting a close-up analysis, regarding further information," South Korea's Office of Joint Chiefs of Staff said in a statement. Acting president Hwang Kyo-ahn convened a national security meeting, South Korea's presidential office said in a text message.
Japanese officials described the launches as a grave threat and said they lodged "strong protests" with nuclear-armed North Korea.
"The launches are clearly in violation of Security Council resolutions. It is an extremely dangerous action," Abe said during lawmaker questions in parliament.
No reports of damage to shipping or aircraft had been received since the launches, Japanese officials said.
The U.S. military did not immediately comment. A U.S. official, speaking on condition of anonymity, said the United States also detected apparent launch activity in North Korea but declined to offer details.