The United States is urging the international community to “redouble its condemnation” of Iran for alleged human rights abuses detailed in a report to be presented to the U.N. General Assembly on Wednesday.

U.S. State Department spokesman Mark Toner says the report by U.N. special investigator Ahmed Shaheed shows Iran is continuing a “brutal repression” of its citizens.

In the report, Shaheed accuses Iranian authorities of secretly executing prisoners without the knowledge of families and lawyers, and detaining political dissidents for prolonged periods, among other abuses. He based the findings largely on interviews with alleged victims of those abuses.

The U.N. Human Rights Council named the former Maldivian foreign minister as a Special Rapporteur on Iran in March, but Tehran has refused to allow him to enter the country.

Toner called on Iran to give Shaheed access to the country immediately. He said Washington stands by the Iranian people, whom he says want to make their voices heard and hold their government accountable for its actions.

The report comes at a time of heightened tension between the United States and Iran. Washington said last week it had broken up a suspected Iranian-backed plot to kill the Saudi ambassador to the United States . Iranian President Mahmoud Ahmadinejad accused the United States of fabricating the plot to try to cause a rift between Iran and Saudi Arabia.