http://news.bbc.co.uk/1/hi/world/mid...st/4271011.stm
Large explosion in southern Iran
An unexplained large explosion has been heard in the southern Iranian province of Bushehr.
There is confusion over the cause of the blast, said to have occurred near the town of Daylam on the Gulf coast.
But an interior ministry spokesman told AP news agency that it may have been caused by a "friendly fire" incident.
There have been eyewitness reports saying a missile was fired by a plane in the area, and that a fuel tank dropped from an Iranian plane.
There have also been reports that a fuel tanker caught fire and exploded.
And some residents said they had heard anti-aircraft fire and the sound of fighter aircraft in the region.
The Mehr news agency quoted a source in the governor's office as saying there had been no air attack on the city.
And in the capital Tehran, a Russian embassy official told the BBC that Russian nationals working in the nuclear plant near Bushehr town had reported that everything was normal, and that they had not heard an explosion.
'Mistaken'
The interior ministry spokesman, Jahanbakhsh Khanjani, told AP: "An airplane flew over Daylam today. Minutes later, there was an explosion.
"But we have no reason to say it's a hostile attack. There is a big possibility that it was a friendly fire by mistake.
"Several such mistaken friendly fire incidents have been reported there in recent days."
Tensions between the US and Iran are running high over what the Americans say is Tehran's attempts to build a nuclear bomb.
Iran says its nuclear programme is entirely peaceful.
Russia has completed construction work at the Bushehr reactor, but it is not yet operational.