In its report overnight, KCNA said North Korea had taken steps for "bolstering the capabilities for self-defense and pre-emptive attacks with nuclear force" in the face of a continued "nuclear threat and blackmail and war drills" by the United States and its "vassal forces."
The North often lashes out at the annual military drills between the United States and South Korea, which the allies describe as defensive in nature.
KCNA accused US President Donald Trump of employing unprecedented hostile policies against North Korea and threatening it with talks of pre-emptive strikes
It described North Korea as an "undeniable new strategic state and nuclear power."
"Do not expect any change in its policy. Its entity as an invincible power can neither be undermined nor be stamped out," KCNA said.
"The DPRK, as a responsible nuclear weapons state, will lead the trend of history to the only road of independence," it added, referring to North Korea by its official name, the Democratic People's Republic of Korea.
N KOREA OIL DEAL PROBE
The crew of a Hong Kong-registered ship have been detained for questioning in South Korea since their tanker was impounded in November for transferring oil to a North Korean vessel and breaching UN sanctions, customs officials said.
The Lighthouse Winmore, which was chartered by a Taiwanese company, was impounded by South Korean customs authorities at the port of Yeosu on November 24 following an inspection.
"Since then, inspectors have been coming on board and questioning the crew", a Korea Customs Service official told AFP.
The Lighthouse Winmore has 25 crew members including 23 mainland Chinese citizens and two Myanmar nationals, another customs official at Yeosu said.
The tanker, chartered by Taiwanese company Billions Bunker Group Corp., previously visited Yeosu on October 11 and loaded up on some 14,000 tonnes of Japanese refined oil before heading towards its purported destination in Taiwan.
Instead of going to Taiwan, however, the vessel transferred 600 tonnes of oil to the North's Sam Jong 2 in international waters off China before returning to Yeosu, the customs service officials said.
Earlier a foreign ministry official in Seoul had said the ship had been seized briefly by customs authorities who inspected it.
Results of the investigation will be reported to the UN Security Council's sanctions committee, foreign ministry officials said.
The Lighthouse Winmore is one of 10 ships the US has asked the Security Council to blacklist for violating sanctions against North Korea.
CHINA OBJECTS TO BLACKLISTING
China objected to the proposal, diplomats said, and only agreed to blacklist four ships. Trump said on Friday that China had been "caught red handed".
The South Korean newspaper Chosun Ilbo cited unidentified officials this week as saying Chinese ships transferred oil to North Korean vessels some 30 times since October.
The article made reference to satellite images released by the US Treasury Department last month, which US officials said showed North Korean vessels attempting to conduct a ship-to-ship transfer.
"North Korea is known to employ deceptive shipping practices, including ship-to-ship transfers, a practice prohibited by [international sanctions against North Korea]," the department said in a statement last month.
The Security Council has imposed three sets of sanctions on North Korea this year: one on August 5 targeting the iron, coal and fishing industries, another set on September 11 aimed at textiles and limiting oil supply, and the most recent on December 22 focused on refined petroleum products.
Pyongyang has slammed the latest sanctions as an "act of war" and on Saturday, the state-run KCNA news agency said in a commentary that the country would continue to pursue its nuclear ambitions.
"The DPRK, an undeniable new strategic state and nuclear power...declares: Do not expect any change in its policy", it said, referring to the North by the abbreviation of its official name.
"Its entity as an invincible power can neither be undermined nor be stamped out."
The Russian Foreign Ministry has also denied claims that UN sanctions against North Korea had been breached by Russian tankers transferring fuel to North Korean tankers at sea.