North Korea launches ballistic missile into sea, says Seoul

North Korea fired an unidentified ballistic missile into the sea off its east coast, South Korea's military said on Thursday.

It's the latest in a series of launches by the nuclear armed country.

A statement from South Korea's Joint Chiefs of Staff (JCS) gave no further details.

The latest launch was announced shortly after the military said South Korea scrambled fighter jets when a group of about 10 North Korean military aircraft flew close to the border dividing the two countries, amid heightened tensions over repeated North Korean missiles tests.

A subsequent statement on North Korea's official KCNA news agency quoted the North Korean military as saying it took "strong military countermeasures" after South Korean artillery fire.

The South Korean JCS statement said the aircraft incident happened late on Thursday and early Friday Korean time.

The statement said the North Korean aircraft were detected flying about 25 km (15 miles) north of the Military Demarcation Line in the central region of the Korea border area and about 12 km (7 miles) north of the Northern Limit Line, a de facto inter-Korean border in the Yellow Sea, between 10:30 pm Thursday (1330 GMT) and 00:20 am (1530 GMT) local time Friday.

It said the aircraft were also seen near the eastern part of the inter-Korean border.

The JCS said the South Korean air force "conducted an emergency sortie with its superior air force, including the F-35A, and maintained a response posture, while carrying out a proportional response maneuver corresponding to the flight of a North Korean military aircraft."