In a response to to sanctioning of Kim Jong Un, North Korea says, US crossed the line

It had already been heavily sanctioned internationally, but, this was the first time Kim Jong Un has been personally sanctioned

North Korea's top diplomat for US affairs said on Thursday that Washington "crossed the red line" and effectively declared war by putting leader Kim Jong Un on its list of sanctioned individuals, and said a vicious showdown could erupt if the US and South Korea hold annual war games as planned next month.

Han Song Ryol, director-general of the US affairs department at the North's Foreign Ministry, said in an interview that recent US actions have put the situation on the Korean Peninsula on a war footing.

The United States and South Korea regularly conduct joint military exercises south of the Demilitarised Zone, and Pyongyang typically responds to them with tough talk and threats of retaliation.

Han said North Korea believes the nature of the maneuvers has become openly aggressive because they reportedly now include training designed to prepare troops for the invasion of the North's capital and "decapitation strikes" aimed at killing its top leadership.

Han says designating Kim himself for sanctions was the final straw.

"The Obama administration went so far to have the impudence to challenge the supreme dignity of the DPRK in order to get rid of its unfavourable position during the political and military showdown with the DPRK," Han said, using the acronym for North Korea's official name, the Democratic People's Republic of Korea.

"The United States has crossed the red line in our showdown," he said. "We regard this thrice-cursed crime as a declaration of war."

Although North Korea had already been heavily sanctioned internationally for its nuclear weapons and long-range missile development programs, Washington's announcement on July 6 was the first time Kim Jong Un has been personally sanctioned.

Less than a week later, Pyongyang cut off its final official means of communications with Washington known as the New York channel. Han said Pyongyang has made it clear that everything between the two must now be dealt with under "war law."

Kim and 10 others were put on the list of sanctioned individuals in connection with alleged human rights abuses, documented by the United Nations Human Rights Commission, that include a network of political prisons and harsh treatment of any kind of political dissent in the authoritarian state.

US State Department officials said the sanctions were intended in part to highlight those responsible for the abuses and to pressure lower-ranking officials to think twice before carrying them out.