North Korea test-fired on Saturday 30 short-range missiles into the sea, in an apparent protest against US-South Korea joint military exercise.

North Korea test-fired on Saturday 30 short-range missiles into the sea, in an apparent protest against US-South Korea joint military exercise.

"North Korea fired off 30 short-range missiles between 4:00 am and 6:10 am (1900-2110 GMT Friday) this morning from its east coast into the Sea of Japan (East Sea)," said a spokesman for the Joint Chiefs.

"The missiles are estimated to have flown about 60 kilometers (37 miles)," he added.

Analysts said the missiles had been launched from the same location as 25 projectiles on Sunday, near the eastern port of Wonsan. The projectiles were Soviet-era short range Frog missiles from the 1960s, they said.

"This is an expression of anger at the joint military exercises" South Korea has been staging with its ally the United States, Professor Yang Moo-Jin of the University of North Korean Studies told AFP.

It is not unusual for Pyongyang to carry out such tests but there has been a spate of them in recent weeks. Saturday's launch was the sixth in just over a month.

South Korea urged North Korea earlier this week to stop what it called "provocative" and potentially dangerous tests.