(Reuters) - North Korea test-fired seven surface-to-air missiles off its east coast on Thursday and its leader Kim Jong Un appeared to have been an observer, South Korea's military said on Friday.

The missiles fell into the sea, said an official at the South Korea's defense ministry.

"We believe they test-fired different kinds of surface-to-air missiles and the longest range is about 200 km (125 miles)," the official said. "It appears Kim Jong Un observed the firing."

The test came as the United States and South Korea finished the first of two large-scale annual military exercises on Friday. The exercise, called "Key Resolve," began earlier this month.

The other joint military exercise, known as "Foal Eagle", will last until April 24, according to the U.S. military.

The exercises anger North Korea, which considers them a preparation for war against it.

The North often tests missiles at the time of the exercises to register its defiance. It also test-fired two short-range missiles at the start of the joint exercises.

North Korea's state media said on Thursday that Kim inspected an island military unit on the east coast, accompanied by his sister, Kim Yo Jong. It made no mention of any missile tests.