CAIRO - A spokesman for the Islamic State said in an undated recording released on Wednesday that an attack on Iranian Revolutionary Guards, which the group claimed on Saturday, would not be the last."The Ahvaz attack will not be the last, God willing," Abi al-Hassan al-Muhajer said in the recording carried by the group's Al Furqan network on Telegram.Gunmen killed 25 people at a military parade in southwestern Iran on Saturday, almost half of them Revolutionary Guards, in one of the worst attacks against the most powerful force of the Islamic Republic. ."The sons of the caliphate have proven just how fragile the security of the Magi State (Iran) is," he said.Reuters could not independently verify the audio recording.Ahvaz National Resistance, an Iranian ethnic Arab opposition movement which seeks a separate state in oil-rich Khuzestan province, and Islamic State have both claimed responsibility for the attack. The latter's news agency AMAQ released a video of three men in a vehicle who it said were on their way to carry out the attack.