UNITED NATIONS, Oct 19, 2011 (AFP) - Up to 200,000 political prisoners are languishing in North Korean prison camps, a sharp increase from 10 years ago, a United Nations envoy said Wednesday.

Compared to 2001, the latest satellite pictures of the country indicate a "significant increase in the scale of the camps," said Marzuki Darusman, the UN Special Rapporteur on the Situation of Human Rights in North Korea, in a report presented before the UN General Assembly.

He noted that some of the prisoners are being held just for being relatives of other detainees.

"I call on the authorities to move forward concretely and urgently on the release of political prisoners," Darusman said.

He pointed to the "critical food situation" in communist North Korea, adding that international food aid was now "dwindling" and that the hermit country "continues to face regular, significant food shortages."

Current government rations meet less than half the needs of most of the population of 16 million receiving public food supplies, Darusman said, citing briefings.

The head of UN humanitarian operations is currently visiting North Korea until Friday to evaluate the country's humanitarian needs.