North Korea 'fires four ballistic missiles'

North Korea has launched four banned ballistic missiles into the waters off the east coast of South Korea, the South Korean military said.

The missiles flew about 620 miles, with three of them landing in Japan's exclusive economic zone, South Korean and Japanese officials said.

The launch comes days after Seoul and Washington started massive joint military drills, which Pyongyang insists are an invasion rehearsal.

Pyongyang has staged a series of missile test-launches of various range in recent months.

The US said it has seen no evidence that the launch involved intercontinental ballistic missiles.

Leader Kim Jong Un is pushing for a nuclear and missile program that can deter what he calls US and South Korean hostility toward the North.

The South's Joint Chief of Staff said in a statement that Monday's launch was made in the Tongchang-ri area in North Pyongan province.

Japanese Prime Minister Shinzo Abe said Monday's firing shows that North Korea has become "a new kind of threat."

Japanese officials said three of the four missiles landed in the 200-nautical-mile offshore area where Tokyo has sovereign rights for exploring and exploiting resources.

The area is the home of the North's Seohae Satellite Station, where it has conducted prohibited long-range rocket launches in recent years.

The nation is banned by the UN from any tests of missile or nuclear technology.

The United States has 28,500 troops stationed in South Korea, and 50,000 in Japan, as a deterrent against a potential aggression from the North.