(CNN) -- A stunning catalog of torture and the widespread abuse of even the weakest of North Koreans reveal a portrait of a brutal state "that does not have any parallel in the contemporary world," a United Nations panel reported Monday. 

North Korean leaders employ murder, torture, slavery, sexual violence, mass starvation and other abuses as tools to prop up the state and terrorize "the population into submission," the United Nations Commission of Inquiry on Human Rights in North Korea said in its report. 

The commission traced the abuses directly to the highest levels of the North Korean government while simultaneously blaming world leaders for sitting on their hands amid untold agony.

"The suffering and tears of the people of North Korea demand action," commission Chairman Michael Kirby told reporters.

The group said it would refer its findings to the International Criminal Court for possible prosecution. It also sent a letter warning North Korean leader Kim Jong Un that he could face prosecution for crimes against humanity.

The government of North Korea -- also known as the Democratic People's Republic of Korea, or DPRK -- rejected the report as a ginned-up effort to undermine its government. 

"It is nothing more than an instrument of political plot aimed at sabotaging the socialist system by defaming the dignified images of the DPRK and creating an atmosphere of international pressure under the pretext of 'human rights protection,'" the government said in a prepared statement. 

The U.N. panel released its 400-page report after hearing from more than 320 witnesses in public hearings and private interviews.

North Korea did not respond to the commission's request for access to the country and information about its human rights practices, according to the commission. 

One witness, a survivor of a North Korean prison camp, told the commission of seeing a guard beat a nearly starving woman who had recently given birth, then force the woman to drown her baby.

Others told of being imprisoned for watching soap operas, trying to find food for their families, traveling without permission or having family members considered suspect by the government. 

"Because we saw so many people die, we became so used to it," one prison camp survivor told the commission. "I'm sorry to say that we became so used to it that we didn't feel anything."

Kirby that he hoped the report would galvanize the world to act.

"We cannot say we didn't know," he said. "We now do know."