A massive explosion and fire rocked a port in southern Iran purportedly linked to a shipment of a chemical ingredient used to make missile propellant, killing five people and injuring more than 700 others. The blast at the Shahid Rajaei port happened as Iran and the United States met on Saturday in Oman for the third round of negotiations over Tehran’s rapidly advancing nuclear programme. Advertisement While no-one in Iran outright suggested that the explosion came from an attack, even Iranian foreign minister Abbas Araghchi, who is leading the talks, on Wednesday acknowledged that “our security services are on high…