UNITED NATIONS — The U.N.’s independent expert on human rights in North Korea warned Thursday that tough U.N. sanctions may be affecting the rights of civilians and called for an assessment of their impact.

Although the sanctions are “not punitive in nature,” Tomas Ojea Quintana told the General Assembly’s human rights committee he is concerned they may be having “a negative impact on vital economic sectors.”

The Security Council has unanimously approved three increasingly tough resolutions this year targeting North Korea’s economy in response to its ballistic missile launches and latest nuclear test.

It has banned North Korea’s exports of coal, iron, lead, textiles and seafood, prohibited joint ventures, and barred any country from authorizing new permits for North Korean workers — all sources of hard currency for the reclusive country.

It has also blacklisted a number of firms in the extraction and financial industries, imposed travel bans and frozen the assets of some government officials, banned the import of natural gas liquids and condensates, and capped the country’s crude oil imports.

Quintana pointed to several examples where sanctions may have prevented access to chemotherapy medicine and other medical supplies, and hindered shipment of wheelchairs and other items needed by the disabled.

In addition, he said, humanitarian organizations are having trouble finding necessary supplies and carrying out international financial transactions.

“History shows us that sanctions can have devastating impact on the civilian population,” he said. “It is my conviction that a comprehensive assessment of the sanctions regime is needed in order to avoid unintended negative impact on human rights, especially economic, social and cultural rights.”

Quintana said an assessment is also needed to ensure “that the sanctions regime does not impose what would effectively constitute a collective punishment on the ordinary citizens of the DPRK,” using the initials of the country’s official name, the Democratic People’s Republic of Korea.

The Security Council has repeatedly expressed regret in its sanctions resolutions that “the DPRK’s massive diversion of its scarce resources toward its development of nuclear weapons and a number of expensive ballistic missiles,” and it has stressed that sanctions “are not intended to have adverse humanitarian consequences for the civilian population.”

In his 22-page report to the General Assembly, Quintana said that North Korea remains “especially vulnerable to food insecurity,” a point also raised by the Security Council.

He cited The International Food Policy Research Institute reporting that 41.6 percent of the population was undernourished in 2014-2016, and 17.9 percent of children were stunted in 2011-2015.

Donors provided only $115 million of the $142 million requested for humanitarian aid for North Korea in 2016, Quintana said, citing reduced interest and “unfavorable political circumstances” for the failure to reach the U.N. target.

He appealed to donors “to ensure that the sanctions regime does not obstruct the timely delivery of international aid.”

Quintana expressed regret that he continues to see “grave violations” of human rights in North Korea.

He cited testimonies of “deplorable conditions” in holding centers where “sexual and gender-based violence are common” against females forcibly repatriated from China, and he noted the impact of corruption on human rights.

Quintana also stressed the impact of corruption on human rights, citing testimonies from North Koreans who said they were required to pay bribes in cash or goods to get access to basic health services, secure employment, travel or avoid punishment after arrest.