STORY: Official news agency IRNA described it as an ammunition factory. The defense ministry said the explosion caused only minor damage, no casualties, and that air defenses had destroyed three attacking drones.

There was no immediate claim of responsibility for the blast.

In July, Tehran said it had arrested a sabotage team made up of Kurdish militants working for Israel who planned to blow up a "sensitive" defense industry center in Isfahan.

In Ukraine, which accuses Iran of supplying hundreds of drones to Russia to attack civilian targets in Ukrainian cities far from the front, a senior aide to President Volodymyr Zelenskiy linked the incident directly to the war there.

"War logic is inexorable & murderous. It bills the authors & accomplices strictly," Mykhailo Podolyak tweeted. "Explosive night in Iran - drone & missile production, oil refineries. Did warn you."