The exercise was carried out by the North's East Sea fleet under the watchful eye of leader Kim Jong-Un, Pyongyang's official Korean Central News Agency (KCNA) reported.
"The ultra-precision anti-ship rocket blasted off from a rocket boat. The intelligent rocket precisely sought, tracked and hit the 'enemy' ship after taking a safe flight," KCNA said, without giving a location or date.
The new anti-ship rocket would be deployed across North Korea's navy "before long", it added.
The nuclear-armed communist country has pushed for the development of new ballistic missiles and rockets, despite heavy sanctions imposed by the international community.
Pyongyang's rhetoric has become increasingly bellicose since the UN passed a resolution condemning North Korea's human rights record and calling for its leaders to be investigated for crimes against humanity, and Washington blamed it for a cyber attack on a US film company.
South Korea and American experts believe the North could be on the way to developing missiles that could threaten the US mainland, although opinion is split on how much progress it has made.
South Korea's defence ministry in January said the North had already made "significant" steps in developing technology that would allow it to equip such a missile with a bomb.
The same month, the US-Korea Institute at Johns Hopkins University released satellite images that offered fresh evidence North Korea is developing a marine-based missile system that would allow it to strike back if hit by a nuclear attack.