Amnesty International has called on Iran to release "immediately and unconditionally" four individuals arrested on December 2 at a gathering marking the 18th anniversary of the killings of two prominent intellectuals.
The London-based rights groups said the four were among a crowd of some 100 people seeking to gather peacefully in a cemetery in Karaj, near Tehran, to commemorate the 1998 killings of prominent intellectuals and writers Mohammad Mokhtari and Mohammad Ja’far Pouyandeh.
The two men were murdered by agents from Iran's Intelligence Ministry. Their deaths were part of a series of extrajudicial killings of Iranian dissidents and intellectuals, which later came to be known as the "chain murders of Iran."
Amnesty quoted witnesses as saying that some of those arrested over the weekend were violently beaten up by the police.
The rights group called on Iranian authorities to ensure that "prompt, independent investigations are conducted into the violent events" of December 2.
The group also said that police and intelligence officials suspected of using unnecessary or excessive force should be held to account.