The United States intends to increase pressure on North Korea to improve its human rights situation, the State Department said Thursday after Secretary John Kerry called strongly for an immediate shutdown of all gulags in the communist nation.

Kerry made the demand in an unusually strong tone in an Asia policy address on Wednesday, saying such deprivation of human dignity "just has no place in the 21st century." He stressed that gulags must be shut down "not tomorrow, not next week, but now."

The top American diplomat also said the U.S. will continue to speak out on the issue.

On Thursday, deputy State Department spokeswoman Marie Harf said the U.S. has long expressed concerns about the "very serious human rights situation" in North Korea.

"When the secretary of state says (it), it carries additional weight. So obviously this is part of our effort to help put pressure on North Korea to change," she told reporters at a regular press briefing.

North Korea has long been labeled one of the worst human rights violators. The communist regime does not tolerate dissent, holds hundreds of thousands of people in political prison camps and keeps tight control over outside information.

But Pyongyang has condemned criticism of its human rights record as a U.S.-led attempt to topple the regime. (Yonhap)