North Korea fired seven surface-to-air missiles into the East Sea from its east coast on Thursday, a day before South Korea and the U.S. ended their annual Key Resolve command post exercise, Seoul’s Joint Chiefs of Staff said Friday.

North Korean leader Kim Jong-un appeared to have observed the live-fire exercise, and the missile launches were conducted without any declaration of a no-sail/no-fly zone to ensure the safety of passing ships and aircraft, the JCS said.

“We believe that the missiles were fired from Seondeok, South Hamgyeong Province, apparently in a show of force against Seoul and Washington, which have been conducting their joint defense drills,” a JCS official told reporters, declining to be identified.

Officials said the communist state fired three kinds of SA missiles: the SA-2 with a maximum range of 47 kilometers, the SA-3 with ranges of 13-35 km, and the SA-5 with a range of about 260 km. Seoul officials said that it was the first time the North had test-launched the SA-5 missile.

Since last month, the North has ratcheted up tension on the peninsula by launching missiles.

On Feb. 6, the North fired four ship-to-ship missiles with a range of 100 km into the East Sea. Two days later, it also launched five tactical missiles with a range of some 200 km. On Feb. 20, the North fired some Silkworm missiles with ranges of 83-95 km in the West Sea.

On March 2 when the Key Resolve exercise kicked off, the North fired two short-range Scud missiles in the East Sea.

The allied Key Resolve command post exercise that involved some 8,600 U.S. troops and 10,000 South Korean troops ended Friday. The Foal Eagle field exercise, which involves 3,700 U.S. troops and 200,000 South Korean troops, will continue through April 24.

By Song Sang-ho (sshluck@heraldcorp.com)