An explosion occurred at Iran's Shahid Rajaee port, resulting in at least four fatalities and over 500 injuries. Israel has denied its involvement. But an investigation is underway.

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

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 four people and injuring more than 500 others.