(CNN) -- A large blast has been reported near the southern Iranian port city of Dailam, in the province where the country has a nuclear power plant, according to Iranian state television.
The television report initially quoted witnesses as saying Wednesday's explosion was the result of a missile fired from a plane seen overhead.
However, it later said the blast could have been a falling fuel tank from an Iranian aircraft.
Rescue teams have been sent to the area, the television said, without providing details on casualties.
Senior Israeli security sources told Reuters news agency that Israel's military was not involved in any blast in Iran.
"There was no Israeli military involvement in this," one Israeli source was quoted as saying.
Iran's Russian-built 1,000-megawatt nuclear reactor, its only nuclear power plant, is due to start operating in Bushehr province in late 2005.
Officials at the Russian Embassy in Tehran told CNN in a phone interview there had been no explosion at the nuclear plant.
Reports of a blast come as Iran's intelligence minister was quoted as saying the United States has been flying spy drones over Iran's nuclear sites.
"Most of the shining objects that our people see over Iran's airspace are American spying equipment used to spy on Iran's nuclear and military facilities," AP quoted Intelligence Minister Ali Yunesi as saying Wednesday
On Sunday, The Washington Post newspaper quoted unnamed U.S. officials as saying the United States has been using unmanned flights for the past year to gather intelligence on Iran's nuclear capability.
"U.S. spying activities over Iranian airspace have been going since a long time ago," AP quoted Yunesi as saying.
"These activities won't reveal anything to them," Yunesi said. "That's to say, it won't give them anything new."
"Our nuclear activities are open and very transparent. Our military activities are all legal," Yunesi said.
"If any of the bright objects come close, they will definitely meet our fire. We possess the necessary equipment to confront them," Yunesi said.
Last month, Yunesi said that the United States had been conducting aerial surveillance, but he neither mentioned drones nor nuclear and military sites, AP reported.
The Iranian air force was ordered in December to shoot down any unknown or suspicious flying objects in Iran's airspace, AP reported. At the time, there were reports in Iranian newspapers that spying devices had been found in a pilotless planes that had been shot down.
Hat Tip: Nuckin' Futz
Syria and Iran plan common front against US: Iran and Syria, both locked in rows with the United States, have said they will form a common front to face challenges and threats.
"We are ready to help Syria on all grounds to confront threats," Iranian Vice-President Mohammad Reza Aref said in Tehran on Wednesday after meeting Syrian Prime Minister Naji al-Otari.
Otari told reporters: "This meeting, which takes place at this sensitive time, is important, especially because Syria and Iran face several challenges and it is necessary to build a common front".
Syria's ambassador to the United States, asked by CNN what the common front with Iran entailed, stressed that it was not an anti-American alliance and said Syria was trying to improve its relations with Washington.
"Today we do not want to form a front against anybody, particularly not against the United States," Imad Moustapha said.
"Syria is trying to engage constructively with the United States ... We are not the enemies of the United States, and we do not want to be drawn into such an enmity," he added.
Washington recalled its ambassador to Syria for urgent consultations on Tuesday to show its deep displeasure with Damascus after Monday's killing of former Lebanese Prime Minister Rafik al-Hariri.
U.S. officials said they were considering imposing new sanctions on Syria because of its refusal to withdraw its 14,000 troops from Lebanon and the U.S. belief that Syria lets Palestinian militants and Iraqi insurgents operate on its soil.
While acknowledging they do not know who was to blame for Hariri's car bomb assassination, U.S. officials argued Syria's military presence and its political power-broking role were generally responsible for Lebanon's instability.
Syria rejects accusations it supports terrorism.
Moustapha told CNN Damascus regarded its military presence in Lebanon as a "stabilising factor" and said "we would be happy to withdraw the troops" if the Lebanese government asked Syria to do so.
Washington has branded Iran part of an "axis of evil" along with pre-war Iraq and North Korea and accuses Tehran of seeking nuclear weapons. Iran says its nuclear programme is solely for electricity generation.
U.S. President George W. Bush has dubbed Iran "the world's primary state sponsor of terror" and has warned the United States could use military action to prevent it acquiring a nuclear bomb.