SEOUL (Reuters) - North Korea launched multiple short-range anti-ship cruise missiles into the sea and Sukhoi jets fired air-to-surface missiles on Tuesday as part of military exercises, South Korea’s military said.

FILE PHOTO: A North Korean flag flies on a mast at the Permanent Mission of North Korea in Geneva October 2, 2014. REUTERS/Denis Balibouse

The missile tests were done on the eve of a national holiday in North Korea to celebrate the birthday of Kim Il Sung, the founder of the country and grandfather of the current leader, Kim Jong Un.

Launched at around 7 a.m. (2200 GMT), the anti-ship missiles plunged into the sea more than 150 kilometres (93 miles) off the east coast town of Munchon, while the Sukhois carried out firing tests, officials at South Korea’s Joint Chiefs of Staff (JCS) told reporters.

The JCS gave no indication of how many missiles were fired, but said a detailed analysis of the launches was being conducted together with U.S. intelligence.

The top U.S. general played down the tests on Tuesday.

“I don’t think it is particularly provocative or threatening to us ... it may be tied to some celebrations that are happening inside North Korea as opposed to any deliberate provocation against us,” Army General Mark Milley, chairman of the Joint Chiefs of Staff, told reporters.

The latest tests were part of wintertime drills the North has been carrying out in recent weeks after coronavirus concerns caused delays, a South Korean military official told Reuters.

“There has been an increase in air force activities which we think was intended to make up for the lack of winter training that they would’ve otherwise wrapped up in late March,” the official said. “And they usually hold military events around the April 15 birthday.”

The official noted that the North used a similar anti-ship cruise missile in June 2017, the last time it was known to have tested such a weapon.

North Korea has been conducting weeks of military drills, including several launches of short-range ballistic missiles. Last month, it fired nine ballistic missiles in four rounds of tests, according to nonproliferation analysts.

On Sunday, North Korean state media reported that Kim Jong Un had visited an airbase and observed drills by fighter jets and attack aircraft.