North Korea has launched two ballistic missiles in the early hours of Wednesday, Tokyo and Seoul both said.

The two missiles appear to have fallen outside Japan's exclusive economic zone, Japanese Defense Minister Yasukazu Hamada said.

He told reporters the first missile reached an altitude of 50 kilometers (31 miles), whereas the second also rose as high as 50 kilometers.

The US military said in a statement the launches pose no immediate threat to US personnel or territory, or to Washington's allies. It added that the United States' commitment to Tokyo's and Seoul's defense remained "ironclad."

What do we know about the launch?

The launch was first reported by South Korea's Yonhap news agency, citing Seoul's Joint Chiefs of Staff.

South Korea said they were analyzing the type of missile fired, adding that it landed in the East Sea, also known as the Sea of Japan between the Korean peninsula and Japan.

The launch is the latest in a string of weapons tests by North Korea, as Seoul and Washington step up their defense cooperation.

Earlier on Tuesday, the two countries announced a port visit to Busan by a US nuclear submarine, for the first time since 1981.

Also on Tuesday, a US service member crossed the border from South Korea into North Korea and was likely now in North Korean custody.

rmt/jsi (AFP, Reuters)