A stray anti-aircraft shell has landed on a minibus in southern Iran, killing two and injuring 13, officials say.
Iran has stepped up its defences of main nuclear facilities
The accident happened during a military manoeuvre near Bushehr, where a controversial nuclear power plant is being built.
A local police chief said the shell had been fired from an air force base outside the city.
He said another shell fired in the same exercise had partially destroyed a house and injured its occupant.
A local official, Ashghar Zareii, said investigations were being carried out into the fatal incident.
"There are reports that the death toll could be as high as seven," he said.
Following efforts by the international community to get Iran to allow full inspections of its nuclear facilities, Tehran has increased the anti-aircraft guard near its main nuclear facilities.
The head of the Bushehr station, Naser Shariflou, said the incident was not linked to the plant.
"No employees from the power plant were killed, there was no terrorist attack on the power plant and the anti-aircraft gun did not shoot because of an attack on the power plant," he told Iran's Irna news agency.
The Bushehr plant does not currently contain any nuclear fuel.
Plans to start up the reactor, which is being built with Russian assistance, have repeatedly been delayed.
Moscow has come under strong pressure from the United States and Israel to drop the project, as Washington accuses Tehran of secretly developing an illegal weapons programme.