SEOUL, South Korea — South Korean jets and navy ships fired a barrage of guided-missiles into the ocean during drills today, a display of military power two days after North Korea test-launched its first intercontinental ballistic missile.

The North's ICBM launch, its most successful missile test to date, has stoked security worries in Washington, Seoul and Tokyo as it showed the country could eventually perfect a reliable nuclear missile capable of reaching anywhere in the United States.

Analysts say the missile tested Tuesday could reach Alaska if launched at a normal trajectory.

The live-fire drills off South Korea's east coast were previously scheduled. In a show of force, South Korea and the United States also staged “deep strike” precision missile firing drills on Wednesday as a warning to the North.

Today's drills were aimed at boosting readiness against possible maritime North Korean aggression.

They involved 15 warships including a 3,200-ton-class destroyer, as well as helicopters and fighter jets, South Korea's navy said in a statement.