(CNN) North Korea said Monday it has decided to close its only direct diplomatic link with Washington, a move made days after the United States slapped sanctions on the country's leader, Kim Jong Un, and other officials over human rights abuses.

Pyongyang and Washington do not have formal diplomatic relations, but North Korea's mission to the United Nations in New York has acted as the main communication conduit between the two countries.

Now it will deal with "DPRK-US relations under the wartime law of the DPRK," according to the Korean Central News Agency (KCNA), North Korea's state-run news agency.

The U.S. sanctions announced last week marked the first time Washington sanctioned Kim personally. Administration officials said Kim was "ultimately responsible" for what they called "North Korea's notorious abuses of human rights."

Pyongyang is already subject to heavy U.S. sanctions for its past nuclear and missile activity. But Wednesday's action marked the first time regime officials had been sanctioned for human rights abuses

"The DPRK government sent the U.S. government a message on July 10 through the DPRK permanent mission to the UN in connection with the fact that the U.S. recently impaired the dignity of the supreme leadership of the DPRK by releasing what they call 'report on human rights,' and 'lists of targets of special sanctions' related to the DPRK," the KCNA reported.

North Korea said it would take "practical actions" against the United States since it "refused to comply" with a demand that the sanctions measure be withdrawn, the KCNA reported Monday. The first phase of "stage by stage" actions would be cutting off the New York contact channel, the report said.

"The DPRK government informed the U.S. government of its principled stand that from now on it would deal with all the issues arising in the DPRK-U.S. relations under the wartime law of the DPRK and the issue of detained Americans is no exception," the article said. "The U.S. is wholly to blame for the ensuing unpleasant things happening in the bilateral times."

North Korea this year has sentenced an American student, Otto Frederick Warmbier, to 15 years of hard labor after accusing him of removing a political banner from a hotel. It also sentenced a South Korean-born American citizen, Kim Dong Chul, to 10 years of hard labor for subversion and espionage.

'Intolerable cruelty'

The United States' new measures were taken in conjunction with the State Department's issuance of a report entitled "Serious Human Rights Abuses or Censorship in North Korea," which was mandated by the U.S. Congress under the North Korea Sanctions and Policy Enhancement Act, passed earlier this year.

A day after the U.S. announcement, North Korea lashed out, calling the move an "open declaration of war against DPRK" and "the worst crime that can never be pardoned," according to KCNA.

The Treasury Department's Acting Under Secretary for Terrorism and Financial Intelligence Adam J. Szubin said in a statement last week that "under Kim Jong Un, North Korea continues to inflict intolerable cruelty and hardship on millions of its own people, including extrajudicial killings, forced labor, and torture."

"Any property or interest in property of those designated by (Office of Foreign Assets Control) within U.S. jurisdiction is frozen," the Treasury Department said. "Additionally, transactions by U.S. persons involving the designated persons are generally prohibited."

The U.S. sanctions also extend to five North Korean state entities, including the Ministry of People's Security, which the Obama administration says oversees labor camps and other detention facilities, where torture, execution, rape, starvation and forced labor takes place. Choe Pu Il, the minister of People's Security, was also named to the list, along with several top officials in the agency.