An explosion has ripped through Qatar's key natural gas export terminal as workers tried to resume operations there after Iran bombed it during the war, causing a fire that injured at least 54 people and left another 18 missing.

An incident during the start-up of operations at Ras Laffan Industrial City resulted in an explosion and fire at the Barzan local gas supply facility on Sunday evening, QatarEnergy said in a statement.

Emergency response teams were deployed to contain the fire, which was now under control, it said.

Qatar's Interior Ministry said in a statement that 54 people had been injured and 18 were missing.

It attributed the explosion to a "technical accident" and said there was no leak that posed a threat to public safety.

It said the Qatari International Search and Rescue Group, in co-operation with the civil defence teams, was conducting search operations for the 18 missing people.

QatarEnergy did not indicate whether the explosion had caused any damage to the plant, which supplies gas to the domestic market.

A Reuters witness earlier reported that a loud boom was heard in the capital Doha, south of the Ras Laffan facility.

The blast could cause further chaos in global energy markets, particularly as Qatar remains one of the world's top natural gas producers.

Qatar shut down its production after Iran's chokehold on the Strait of Hormuz meant it couldn't get shipments out to its clients.

With Iran loosening its grip on the strait as negotiations continue over a permanent end to the war, Qatar began work to try to restart its export terminal.

That work sparked an explosion and fire at the Barzan gas supply facility, the state-run firm QatarEnergy said.

with AP