Afghanistan — Hundreds of oil and gas tankers have been destroyed by fire in a "catastrophe” at Afghanistan’s biggest trade crossing with Iran, causing millions of dollars of losses, officials said on Sunday.

The huge blaze, which broke out Saturday afternoon at Islam Qala Port 120 kilometres from the western city of Herat, has been contained and an investigation launched into its cause.

"We were told that 100 or 200 tankers have been destroyed, but this number could be higher,” Jailani Farhad, spokesman for the governor of Herat province, said after visiting the scene.

Younus Qazi Zada, the head of the Herat Chamber of Commerce, said 500 tankers had been engulfed by flames.

"Around $50 million of damage has been caused by the fire, but a more accurate figure will be available in the coming days,” he added.

"The catastrophe was much bigger than imagined,” he said.

Around 20 people were injured in the fire, according to Herat health officials.

Videos posted on social media on Saturday night showed the towering fire and huge clouds of thick black smoke billowing into the sky.

During the blaze looters descended on the site, stealing goods that were being imported and exported across the border.

Security forces on Sunday opened fire on a vehicle, killing one man, after the driver failed to stop at a checkpost that had been hastily set up to prevent suspected looters from entering what was left of the customs office compound.

An AFP photographer said hundreds of people had gathered at the site, trying to get access to the trucks.

The finance ministry said early findings suggested the blaze started in a tanker before quickly spreading and causing "heavy financial losses” — including fuel, tankers and customs facilities.

Damage to power lines from the incident left large parts of Herat province without power on Sunday.

Islam Qala is one of the major ports in Afghanistan, through which most official trade with Iran is conducted.

Kabul has waivers from Washington allowing it to import oil and gas from Iran despite US sanctions.

Iranian foreign ministry spokesman Saeed Khatibzadeh said the border "was held open for trucks, cars and people running from the fire”.

Afghanistan’s vice president Amrullah Saleh said hundreds of trucks were allowed to enter Iran to escape.

Traders have been asked to use alternative border crossings.

The Taliban has regularly attacked fuel tankers they suspect of supplying foreign troops in the country.

In 2014, the hardline group destroyed more than 200 fuel trucks on Kabul’s outskirts in an attack.

There was no indication that militants were behind Saturday’s blaze.

However, insurgents assaulted a nearby security post shortly after the blaze broke out, taking advantage of the situation, the spokesman for the governor of Herat province said Saturday.

Security forces have been deployed around the port area.

Afghanistan has been hit by a surge in violence despite ongoing peace talks between the Taliban and the Afghan government, which have so far failed to achieve a breakthrough.

The rise in violence has led US President Joe Biden’s administration to launch a review of a deal signed between Washington and the terror group last year that paved the way for the withdrawal of all American troops in the coming months