South Korea confirmed today that rival North Korea fired four short-range Scud missiles into the sea a day earlier in an apparent attempt to protest against ongoing US-South Korean military exercises that Pyongyang calls a rehearsal for invasion.

The launches, however, weren't expected to raise tension as North Korea routinely tests short-range missiles and it has recently sought better ties with South Korea in what outside analysts say is an attempt to win badly needed foreign investment and aid. The rival Koreas this month held their first reunions of Korean War-divided families in more than three years.

Four projectiles with a range of more than 200 kilometres landed off the North's eastern coast yesterday, and South Korean Defense Ministry spokesman Kim Min-seok told reporters today that an analysis of their speed and trajectory showed they were Scud missiles.

Defense officials also confirmed reports that North Korea fired four other short-range KN-02 missiles with a range of about 100 kilometres off the east coast one week ago.

Mr Kim said South Korean officials didn't disclose last Friday's launches because North Korea frequently test-launches missiles with a range of less than 100 kilometres. But Kim said Scud-series missiles, which are capable of hitting all of South Korea, are a security treat and yesterday's Scud launches were the first of that kind since 2009.

He said there are no signs that North Korea is preparing for additional missile launches.

Analysts said the launches were largely aimed at protesting the South Korea-US military drills that began Tuesday and won't be a prelude to a spike in tension between the rival Koreas.

"The launches were a test designed to improve its missile capability and also an armed protest against the drills," said analyst Cheong Seong-jang at the private Sejong Institute in South Korea. "But we already know (they have Scud missiles) ... We also have such a level of missiles. The launches didn't have special meaning."

Last year, North Korea furiously reacted to the same South Korean-US military drills by issuing a torrent of fiery rhetoric and threats to launch nuclear missiles against Seoul and Washington. Last year's drills came after North Korea conducted its third nuclear test. The US took the unusual step of sending nuclear-capable bombers in a show of its resolve to protect its ally.

North Korea hasn't issued any harsh rhetoric against the current drills after their start. Seoul and Washington have said the annual drills are defensive in nature.