LOADING ERROR LOADINGDUBAI (Reuters) — Plainclothes Iranian security forces have rounded up thousands of people in a campaign of mass arrests and intimidation to deter further protests after crushing the bloodiest unrest since the 1979 Islamic Revolution, sources told Reuters. AdvertisementAuthorities cut internet access and stifled the unrest with overwhelming force that killed thousands, according to rights groups. Within days, plainclothes security forces launched a campaign of widespread arrests accompanied by an intensified street presence based around checkpoints, according to five activists who spoke on condition of anonymity from inside Iran. Judiciary officials have warned that “those committing sabotage, burning public property and involved in armed clashes with security forces” could face death sentences. Mai Soto, the U.N. Special Rapporteur on Iran, said the thousands of detainees included doctors and healthcare workers.