WASHINGTON (Yonhap) -- A senior U.S. senator formally requested the Barack Obama administration Sunday to pay more attention to North Korea's political prison camps often compared with the Soviet gulag or even the Nazi concentration camps.

In a statement posted on his Web site, Sen. Patrick Leahy (D-VT) said trying to resolve Pyongyang's nuclear program is one thing and speaking out about its human rights abuse is another. He is the chairman of the Senate Judiciary Committee.

"We have vital national security interests at stake in our dealings with the North Korean regime, which has acquired nuclear weapons. I am one who believes that we can fully and effectively pursue these interests through diplomacy and other means, without having to mute our outrage about human rights atrocities like these," he said.

His statement came as the U.S. marks the Holocaust Days of Remembrance, an annual event to commemorate the victims of the mass genocide by Nazi Germany during World War II.

Obama is scheduled to visit the U.S. Holocaust Memorial Museum in Washington on Monday, where he will deliver a speech and make a tour.

"Let us individually and together similarly raise our voices against the crimes against humanity that are taking place behind the walls and barbed wire of North Korea's labor camps, where some one in four people die each year -- starved to death, or worked to death, or executed," the senator said.

"Let it not be said by future generations that though we knew enough, we did not care enough to condemn and to lend our efforts to end this brutal system."

An estimated 150,000 to 200,000 North Koreans are incarcerated in the North's secretive gulags, which can be seen via satellite, according to the U.S. Committee for Human Rights in North Korea, a Washington-based nongovernmental organization.

Human rights activists here call for the United Nations to step up efforts to address the issue.

They say the U.N. needs to establish an inquiry commission to look into crimes against humanity at those prison camps.