SEOUL: North Korea's military fired short-range missiles into the East Sea (Sea of Japan) on Friday, Yonhap reported, at a time of heightened tensions following Pyongyang's recent nuclear test.

A single unit of the North's military test-fired the missiles presumed to be KN-02, estimated to have a range of about 120 kilometres (74 miles), the report said.

"The launch was seen as testing its capability for short-range missiles. It seemed to be conducted on a military-unit level, not at a national level," said a military source in Seoul cited by the South Korean news agency.

The South's defence ministry declined to confirm the report.

The tests came a day after North Korea's leader Kim Jong-Un oversaw a live-fire artillery drill near the disputed Yellow Sea border with South Korea, as the South's prime minister visited the flashpoint area.

The area has witnessed bloody North-South clashes in the past and, with military tensions at their highest level for years, is seen as the prime location for another confrontation.

Kim made an inspection tour of the same artillery units last week that was widely covered by state TV and the Korean Central News Agency (KCNA).

North Korea has threatened to unleash a second Korean War -- backed by nuclear weapons -- in response to UN sanctions imposed after its third atomic test in February and joint South Korea-US military manoeuvres.

So far, the land and sea border dividing the two Koreas has remained calm, if tense, and the South has dismissed the North's threats as a crude attempt to put "psychological pressure" on Seoul.