In Iran, four people have been arrested after a state prosecutor was shot dead outside his home in northern Iran.Vali Hajgholizadeh, who is reported to have a reputation for fighting corruption, was killed in the town of Khoy near the Turkish border. Two gunmen opened fire on Hajgholizadeh outside his house late yesterday and he died of his wounds in hospital. The Iranian state Press TV station reported Hajgholizadeh had received death threats in the last few days. Local officials said a Kurdish separatist group had claimed responsibility for the killing. The region has been the scene of frequent clashes with Kurdish groups who want to establish their own state.