North Korea has test fired seven missiles into the sea, according to officials.

The surface-to-air missiles launched from North Korea late yesterday flew into waters off the eastern coast, the South Korean defence ministry has said.

North Korea routinely test launches missiles, rockets and artillery but the latest launch came as South Korea and the US conducted annual drills that Pyongyang calls an invasion rehearsal.

Seoul and Washington say the drills are for defence.

North Korea fired two short-range missiles on the first day of the drills earlier this month and warned of "merciless" strikes against South Korea and the US.

The military exercises are scheduled to continue until late April.