After a new round of UNSC sanctions against its nuclear program, North Korea says it will continue to weaponize its spent plutonium rods and to take "resolute military actions" against efforts to isolate it.

In a statement on Saturday, an unnamed spokesman for Pyongyang's Foreign Ministry said the country can no longer "even think about giving up its nuclear weapons".

It added that Pyongyang had weaponized more than one third of its spent plutonium rods and would begin a new program to enrich uranium.

"Firstly, all plutonium to be extracted will be weaponized. One third of used fuel rods have so far been reprocessed," read the statement. "Secondly, we will start uranium enrichment."

Earlier on Friday, the UN Security Council imposed tougher sanctions against the country over its most recent nuclear test. The sanctions include a wider ban on arms sales and the inspection of North Korean ships.

Tension in the troubled Korean peninsula has built up since May 25, when Pyongyang staged it second nuclear test and fired a series of short-range missiles.

Senior officials in Washington have said that the US will do what it deems necessary for the security of its allies in the troubled region.

North Korea said it would view any US-led attempts to "blockade" it as an "act of war".

JR/SC/MD