The seven ground-to-air missiles flew into the sea off the eastern coast of North Korea after being fired from a site near the eastern town of Sondok, South Korea's Defense Ministry said on Friday.

A ministry spokesman said the exercise late on Thursday was supervised by North Korean leader Kim Jong-Un.

The operation came amid a surge in tensions between the two Koreas as the United States and South Korea conduct military drills that Pyongyang considers to be a rehearsal for invasion.

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

Any ballistic missile test by the North is banned by UN resolutions.

'Critical' drills

One of the joint drills, Key Resolve, ended on Friday, but the other, Foal Eagle, is scheduled to continue until April 24.

The commander of the allies' combined Forces Command, Gen. Curtis Scaparrotti, said on Friday that the Key Resolve exercise - a largely computer-simulated drill to run through a range of conflict scenarios - was "critical" for South Korea's security.

The two Koreas remain technically at war after the 1950-53 Korean conflict ended with a ceasefire rather than a peace treaty.

tj/sms (AFP, AP)