SEOUL, South Korea — South Korean warplanes and navy ships have fired a barrage of missiles into the waters during one-day drills aimed at boosting readiness against possible North Korean aggression.

Thursday’s drills off the east coast were previously scheduled but they occurred two days after North Korea test-launched its first intercontinental ballistic missile.

South Korea’s navy says the drills involve 15 warships including a 3,200-ton destroyer, helicopters and fighter jets.

The North’s ICBM launch was a milestone in its efforts to pursue an arsenal of long-range nuclear missiles capable of reaching anywhere in the United States. Analysts say the missile tested Tuesday could reach Alaska if launched at a normal trajectory.

After the launch, North Korean leader Kim Jong Un said he will never put his weapons programs up for negotiations.