The new United Nations investigator for Iran has warned of a “dramatic increase” in government-ordered executions and other grave human rights abuses in the Islamic Republic.

In a U.N. report issued Wednesday, special investigator Ahmed Shaheed said more than 200 officially announced executions have taken place in Iran so far in 2011, including 83 in January alone. He accused Iranian authorities of conducting more than 300 secret executions at Vakilabad prison in 2010 without the knowledge of families or lawyers.

Shaheed also said Iran has been detaining political dissidents for prolonged periods and persecuting religious and ethnic minorities. He based his findings largely on interviews with victims of state-sponsored abuse because Tehran has refused to allow him into the country.

The U.S. Wednesday urged the international community to “redouble its condemnation” of Iran for the alleged crimes. State Department spokesman Mark Toner said the report shows Iran is continuing a “brutal repression” of its citizens. He called on Iran to give Shaheed immediate access to the country.

The U.N. Human Rights Council named Shaheed as a Special Rapporteur on Iran in March. Also Wednesday, Iran's judiciary ordered an investigation into human rights crimes allegedly committed by the U.S.

Iran's judiciary chief, Ayatollah Sadeq Larijani, said he has assigned the country's state prosecutor to gather evidence proving U.S. crimes in Iran and elsewhere.

The U.N. 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.