A massive explosion and fire rocked a port Saturday 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.

Five people have been killed and more than 700 injured in a huge explosion at the port of Bandar Abbas in southwestern Iran, according to official Iranian media and emergency services.

The blast occurred as Iran began a third round of nuclear talks with the United States in Oman. The cause wasn't immediately clear.