Iran's Revolutionary Guards have arrested prominent lawyer Mostafa Nili, one of more than a dozen rounded up amid a crackdown on protests sparked by Mahsa Amini's death, his sister said.

Guards intelligence agents detained Nili at Tehran's Mehrabad international airport on Monday night before raiding his mother's house and taking him into custody, Fatemeh Nili tweeted.

Another prominent lawyer, Saeid Dehghan, who is believed to be abroad, confirmed his arrest in a post on Twitter.

Nili was one of the "few hopes for citizens against a political system that is the enemy of lawyers" as well as against the Islamic Revolutionary Guard Corps who "consider themselves the law", Dehghan said.

Security forces have waged a campaign of mass arrests that has netted artists, dissidents, journalists and lawyers since protests broke out over Amini's death on September 16.

Amini, 22, died three days after falling into a coma when she was arrested by the notorious morality police in Tehran for allegedly flouting Iran's strict dress code for women based on Islamic sharia law.

Security forces, including the Guards, have killed at least 186 people during the crackdown on the women-led protest movement, the Norway-based group Iran Human Rights says.

At least another 118 people have lost their lives in distinct protests since September 30 in Sistan-Baluchistan, a mainly Sunni Muslim province on Iran's southeastern border with Pakistan.

Thousands of people have been arrested in the crackdown, including more than a dozen lawyers who had been working to defend those taken in before being detained themselves.