The report by the Human Rights House of Iran (HRHI), which is based outside Iran, says at least 1,256 people including students and journalists were arrested in the period.
HRHI's Mojtaba Samienejad told Radio Farda that those arrested include 185 students*, 165 members of religious minorities, 129 political activists, 129 Kurdish activists, 43 journalists and bloggers, 40 Turkoman activists, 22 labor activists, 20 human rights activists, eight women's rights activists, and eight Arab activists.
Most were detained in Tehran, the center of most of the protests.
Samienejad said the number of people detained does not include those whose arrests were not made public by their family members or the judicial authorities.
"Obviously, providing the total number of detainees in Iran is impossible," Samienejad said. He said that is because there is no free access to relevant information about detainees and because prisoners and their families could be endangered if they go public with such information.
He added that many other people were arrested or detained between February 20 and March 20, but the authorities have provided almost no information about those detentions.
That includes unconfirmed reports that opposition Green Movement leaders Mir Hossein Musavi and Mehdi Karrubi and their wives had been detained by security forces during that time.
* CORRECTION: This story initially said 85 students had been jailed; the correct figure is 185.
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