SEOUL, South Korea (AP) — North Korea said today it fired long-range strategic cruise missiles into the sea to test the country’s nuclear deterrence, days after it showed apparent progress in the construction of its first nuclear-powered submarine.

Sunday’s launches were the latest weapons display by North Korea ahead of its planned ruling Workers’ Party congress early next year. Keen outside attention on the congress, the first of its kind in five years, will be on whether North Korean leader Kim Jong Un will establish new priorities in relations with the U.S. and respond to Washington’s calls to resume long-dormant talks.

The official Korean Central News Agency reported that Kim expressed “great satisfaction” over Sunday’s launches, which occurred off the country’s west coast. It said Kim noted that testing the reliability of North Korea’s nuclear deterrence and demonstrating its might are “just a responsible exercise of the right to self-defense and war deterrence” in the face of external security threats.

South Korea’s Joint Chiefs of Staff said it was aware of several cruise missile launches made from North Korea’s capital region on Sunday morning. It said South Korea maintains a readiness to repel any potential North Korean provocations through its alliance with the United States.

U.N. Security Council resolutions prohibit North Korea from launches involving its huge stockpile of ballistic missiles.

Its cruise missile tests aren’t banned, but they still pose a threat to the U.S. and South Korea because they are highly maneuverable and fly at low altitudes to avoid radar detection.