About 3,700 people were arrested in the protests and unrest that shook Iran over the past two weeks, according to a reformist MP – a far higher number than authorities had previously said.

The protests, which vented anger at high unemployment and official corruption, were the largest in Iran since the disputed 2009 presidential election, and included calls for the overthrow of the government.

At least 21 people have been killed in the unrest surrounding the protests.

The official news website of the Iranian parliament, icana.ir, quoted Mahmoud Sadeghi of Tehran as saying different security and intelligence forces detained the protesters, making it difficult to know the exact number.

He did not elaborate nor did he say where he got the figure. Previously, authorities had said “hundreds” were arrested in Tehran alone, not offering a total figure for arrests as the demonstrations spread into the Iranian countryside. Many are frustrated at President Hassan Rouhani’s failure to improve people’s economic or social circumstances.

Interior minister Abdolreza Rahmani Fazli has said about 42,000 people took part in the protests.That would mean nine per cent of those who demonstrated were arrested.

Tehran prosecutor Abbas Jafari Dolatabadi said 70 of the detained protesters had been freed on bail. There would be more releases, except for the main instigators of the riots who would be “dealt with seriously”.