A senior State Department official says Iranian forces may have killed more than 1,000 people in response to recent protests that have swept the country.
Special Representative for Iran Brian Hook cited unspecified reports and provided no evidence of the death toll.
Amnesty International recently said more than 200 people were killed in the recent unrest over economic hardship.
Hook told reporters at the State Department on Thursday the U.S. has seen video of one incident in which more than 100 people were shot and killed.
Hook also responded to questions related to US Navy seizing suspected Iranian missile parts set for Yemen.
“One of the many deficiencies of the Iran nuclear deal is that it ended the prohibition on Iran's ballistic missile testing. That was one of the concessions that was made. It was a mistake and we are trying to restore that, among other things,” he said.
Hook said that a Navy warship seized a “significant hoard “of suspected Iranian guided missile parts headed to rebels in Yemen.
“The weapon components comprise the most sophisticated weapons seized by the U.S. Navy to date during the Yemen conflict,” he added.
The seizure from a small boat by the U.S. Navy and a U.S. Coast Guard boarding team happened last Wednesday in the northern Arabian Sea.