North Korea has fired at least one ballistic missile into the sea.

North Korea has fired at least one ballistic missile into the sea, Yonhap news agency reported on Wednesday (local time), hours after an American nuclear-armed submarine made its first South Korean port call in decades.

The launch was reported by South Korea's Joint Chiefs of Staff, according to Yonhap, who said they were still analysing what type of missile had been fired, and that it had landed in the East Sea, also known as the Sea of Japan.

Japan's Coast Guard said a second missile may also have been launched, according to Kyodo news agency.

The launch is the latest in a series of weapons tests by Pyongyang, and comes as Seoul and Washington ramp up defence cooperation in the face of soaring tensions with the North.

On Tuesday, they held the first Nuclear Consultative Group meeting in Seoul and announced an American nuclear submarine was making a port visit to Busan for the first time since 1981.

The move had been expected to trigger a strong response from North Korea, which baulks at having US nuclear assets deployed around the Korean peninsula.