A massive explosion and fire in Iran's largest commercial port killed at least 40 people and injured more than 1,000, a provincial official has said.

"For the moment, 40 people have lost their lives as a result of injuries caused by the explosion," Hormozgan provincial official Mohammad Ashouri told state television on Sunday after the Saturday blast in Shahid Rajaee Port near the strategic Strait of Hormuz.

On Saturday, a fire broke out around 12 pm local time (0830 GMT) at Shahid Rajaee Port, specifically in the container dock area, according to local media.

Initial reports suggested the presence of flammable materials near the site of the explosion.

Quoting witnesses, reports indicated that the minor fire quickly spread and triggered the explosion due to the 40 degrees Celsius heat and the accumulation of flammable substances.

The strategically important port, located in the southern Hormozgan province, lies about 15 kilometres (9.3 miles) southwest of the port of Bandar Abbas on the northern shore of the Strait of Hormuz.

‘Heartbreaking’

Iran's Supreme Leader Ali Khamenei has called for an investigation into the explosion.

In a statement on Sunday, he described the incident as "heartbreaking" and said it has caused "deep sorrow and concern," urging security and judicial authorities to conduct a full probe in order to "uncover any negligence or deliberate wrongdoing, and pursue it in accordance with the law."

"All officials must consider themselves responsible for preventing such tragic and damaging incidents," the statement read.

On the other hand, Russian President Vladimir Putin ordered the immediate deployment of emergency specialists to Iran to assist Iranian authorities in containing the fire at the port after a request from Tehran, the Russian Embassy announced on Sunday.

According to the embassy, several aircraft carrying teams from the Russian Ministry of Emergency Situations are being dispatched to Iran.

“We wish success to the Russian rescuers and their Iranian counterparts in containing the fire and saving this strategic port for the Iranian economy and the lives of the people,” the embassy said.