At least four people have been killed and 500 more injured in a massive explosion at a port near the southern Iranian city of Bandar Abbas, state media is reporting.

The blast took place at the Shahid Rajaee port on Saturday morning, blowing out the windows of nearby office buildings and causing the roof of at least one building to collapse.

Footage showed people fleeing from the wharves at the time of the explosion and others lying wounded on the street. There are also reports of people being trapped under collapsed walls.

A fire is still raging at the container terminal site and pictures show huge clouds of black smoke billowing over the wharfs.

Authorities dispatched helicopter crews to try and extinguish the flames, while the injured were being rushed by medics to nearby hospitals, authorities said.

Some workers are ?still trapped under collapsed roofs and ?we are trying to rescue them?, one official told local media according to BBC Persian.

Footage shared online shows people bracing at the point of explosion and then fleeing the area.

According to reports, witnesses say the explosion occurred after a fire broke out and spread to unsealed containers storing ?flammable materials?, most probably, chemicals.

?The source of this incident was the explosion of several containers stored in the Shahid Rajaee Port wharf area,? a crisis management official in the region said.

One analyst firm said it believed the affected containers had contained solid fuel for Iranian missiles.

The fire had been the result of ?improper handling of a shipment of solid fuel intended for use in Iranian ballistic missiles,? according to Ambrey Intelligence, a global maritime risk firm.

The firm said it had found 12 merchant vessels within five nautical miles of the explosion when the incident occurred, seven of which had been berthed at the port at the time.

Shahid Rajaee is Iran?s largest commercial port, located on Iran?s southern coast close to the Strait of Hormuz, a major shipping channel for oil cargo.

It is located about 20km (12 miles) west of Bandar Abbas, the capital of the Hormozgan province.

Iran?s national oil production company said the explosion at the port had ?no connection? to the country?s oil refineries, fuel tanks and pipelines, local media reported.

The explosion was so large residents reported hearing and feeling the explosion from 50km (31 miles) away.

Iranian President Masoud Pezeshkian has expressed his ?deep regret and sympathy? for victims and has announced a government investigation. (BBC)

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