The body of the nephew of Iran's opposition leader — slain in the deadliest day of anti-government protests in months — disappeared from hospital yesterday, and security forces detained at least seven prominent activists, according to opposition reports.

Iranian state television said that eight people had died in Sunday's street violence, but independent confirmation of the casualty toll was virtually impossible because of curbs on media coverage. Tehran residents say restrictions on internet access were intensified and Iranians were unable to see opposition websites. Cell phone and text messaging services were sporadic.

Reza Mousavi said that the body of his brother Ali Mousavi was taken overnight from a Tehran hospital and that nobody had accepted “responsibility” for removing the corpse. Authorities were possibly seeking to deter mourners from organising more protests around the funeral.

The slain man was the nephew of opposition leader Mir Hossein Mousavi, a presidential contender in a disputed election in June.

Sunday's bloodshed drew harsh condemnation from another opposition leader who compared the current Ahmadinejad government to the dictatorship that was ousted by the Islamic Revolution three decades ago.

In an online statement, Mahdi Karroubi, another candidate in the June election, asked how the government could spill the blood of its people during commemorations of Shia Islam's most important observance, Ashoura. He told the opposition Rah-e-Sabz website that even the former government of the hated Shah, who was overthrown in 1979, respected the holy day, and described those who confronted the protesters as “savage individuals”.

The government crackdown drew sharp criticism from the West, which is already locked in a dispute with Iran over its suspected efforts to develop nuclear weapons. Iran says its nuclear programme is for peaceful purposes.