TOKYO: North Korea has test-fired a ballistic missile which landed in Japanese waters, South Korea and Japan say on Wednesday.

The missile was launched off the North's east coast early on Wednesday and travelled about 1,000km (620 miles), one of the North's longest launches to date.

Japanese PM Shinzo Abe said it was a "grave threat" to his country.

The North is barred from developing nuclear and ballistic missile technology by UN resolution.

But it had vowed a "physical response" after the US and South Korea agreed plans to deploy an advanced US missile defence system in South Korea.

The North has carried out repeated missile tests in recent months.

The US Strategic Command said two missiles had been fired simultaneously on Wednesday from Hwanghae province at about 07:50 Seoul time on Wednesday, but one exploded immediately after launch.

The Japanese defence ministry said the other missile landed inside its exclusive economic zone (EEZ) - the 200 nautical miles of ocean around a country over which it has jurisdiction.

An official at South Korea's Joint Chiefs of Staff said it appeared to have been a medium-range Rodong.