North Korea's ambassador to the UN condemned the U.S.' recent seizure of a North Korean cargo ship, calling on the U.S. to return the ship without delay.

Kim Song, the North's permanent representative at the UN, made the call on Tuesday in a rare news conference at the UN headquarters in New York, criticizing the U.S.' seizure as a "heinous act."

Kim said that his country is condemning "in strongest terms" the seizure of the ship since it is an early product of the U.S.' extreme hostile policy against the North. 

The envoy said unilateral sanctions and the extraterritorial application of national jurisdiction of a third country cannot be justified in any case, and in any circumstance and under international law.

Kim noted the U.S. should think about the consequences the seizure could have on future developments, adding Pyongyang will "sharply watch every move of the U.S." 

The U.S. Justice Department said on May 9th that it had impounded the "Wise Honest," a vessel suspected of violating U.S. domestic law and international sanctions. It is the first time that American authorities have directly seized a North Korean ship.