SEOUL (REUTERS) - North Korea on Thursday (Dec 14) warned it would take "merciless self-defensive" measures should the United States enforce a naval blockade, which Pyongyang sees as "an act of war", the isolated nation's state media said.

Citing a foreign ministry spokesman, the North's KCNA news agency said a naval blockade would be a "wanton violation" of the country's sovereignty and dignity.

US President Donald Trump was taking an "extremely dangerous and big step towards the nuclear war" by seeking such a blockade, it added. It was not immediately clear what US proposal the agency was referring to.

"Should the United States and its followers try to enforce the naval blockade against our country, we will see it as an act of war and respond with merciless self-defensive counter-measures as we have warned repeatedly," the agency said.