Unconfirmed reports have suggested that Israeli agents were behind an explosion at an Iranian military base that killed 17 soldiers, including at least one highly-placed official with responsibility for missile technology.
Iran's Revolutionary Guard said that the blast occurred on Saturday when weapons were being moved to an arms depot close to the village of Bidganeh, 25 miles southwest of the capital Tehran.
According to the BBC the blast was heard up to 25 miles away, and fires raged in the base for more than two hours after the initial explosion.
Local MP Hossein Garousi said on a parliamentary website that "a large part of an ammunition depot exploded".
An earlier death toll of 27 was later revised down by the Revolutionary Guard to 17, with 16 others reported injured.
One of those killed was Brigadier General Hassan Moghaddam, who was responsible for "industrial research aimed at ensuring self-sufficiency of the Revolutionary Guards".
According to reports his brief also stretched to a wider responsibility for Iran's missile armaments as a whole.
Iranian officials have not said what caused the explosion, but several newspapers have claimed it was the work of outside agents, possibly the Israeli covert operations agency Mossad.
One US-based blogger known for his contacts in the Israeli military said that the blast was an act of sabotage carried out in conduction with the People's Mojaheddin of Iran (MEK), an exiled opposition group.
Richard Silverstein said via his website that "it is widely known within intelligence circles that the Israelis use the MEK for varied acts of espionage and terror" and that Israeli sources had confirmed the country was involved.
Silverstein has since claimed he has been subject to "menacing threats" since reporting the comments.
Mossad and Israel do not claim responsibility for such attacks, and the MEK have denied involvement.
However commentators have pointed to a recent trend of suspicious attacks on Iranian officials with links to a possible nuclear programme.
In 2010 a scientist was killed after his car was blown up with so-called "sticky bombs" by assailants on motorcycles.
A computer worm which targeted Iranian nuclear enrichment systems was also believed to have been the work of Israel working with the US, Britain or other nations.
Tensions have risen in recent weeks over Iran's alleged attempts to enrich enough nuclear material to build a nuclear weapon.
A report from the International Atomic Energy Agency last week claimed that the country had made significant progress towards building a nuclear weapon, leading to a step-up in contingency planning by UK and US authorities over theoretical pre-emptive strikes.