Amnesty International, in a 70-page report, said it had evidence to suggest there were four times as many public executions in Iran last year than there were in 2010. Most of those sentenced to death in Iran are executed by public hangings.
"Public executions are believed to have quadrupled in 2011 in what may be a strategy to spread fear among the population and to deter protests," the Amnesty International report said. "As the repression of dissenters widens, the risk of further death sentences and executions cannot be excluded."
Iran responded with force when the so-called opposition Green Movement led a popular uprising against Iranian President Mahmoud Ahmadinejad's re-election in 2009. Opposition leaders Mir Hossein Mousavi and Mehdi Karroubi have been under house arrest for more than a year.
Amnesty International said Iranian authorities have "cranked up repression in law and practice" since the controversial 2009 election.
There are more than 3,400 candidates competing for 290 seats in the Iranian Parliament in Friday's election. The Daily Telegraph newspaper in London reported that Iran's Supreme Leader Ayatollah Ali Khamanei called on supporters to rally against the president.
Ahmadinejad fell out of favor with the ruling cleric after the 2009 election.