Conflicting reports have emerged from Iran over an explosion heard in the central city of Isfahan, close to the country's sensitive nuclear facilities.

Iran's semi-official Isna news agency quoted a judiciary official in Isfahan, saying that an explosion had been heard.

"We heard a sound similar to that of an explosion but we have received no reports about its causes and the consequences so far," said Gholamreza Ansari, in quotes carried by Isna. He said the explosion did not appear to be of any significance.

Iran's semi-official Fars news agency was one of the first media organisations to report the explosion, saying it was heard at 2.40pm local time (1110 GMT). Fars quoted the deputy governor, Mehdi Ismaili, as confirming a sound that the news agency reported was loud enough to be heard across the city. The agency, however, removed the article from its website sometime later.

Ismaili then spoke to another semi-official agency, Mehr, denying his quotes as reported by Fars. "I have heard no sound whatsoever in Isfahan," he said. Ismaili also told the Irna state news agency that he had not spoken to Fars in the first place.

Several residents of Isfahan told the Guardian that they had heard a loud blast. One said that it rattled the windows of their home.

Isfahan is home to Iran's uranium conversion facility (UCF), which operates under IAEA surveillance. Iran's main uranium enrichment facilities are situated in the city of Natanz to the north-east of Isfahan, where many of the country's centrifuges are installed. In recent years, Iran's nuclear activities at Natanz have been at the centre of an international dispute.

Earlier this month, a huge explosion at a missile base in the west of Tehran killed more than 30 members of Iran's revolutionary guards, including Major General Hassan Tehrani Moghaddam, a senior commander described as the architect of the country's missile programme.

In recent years, Iran's nuclear and missile programmes have experienced a series of setbacks in what has been widely seen as a covert war against the Islamic republic.