A massive explosion took place Saturday at an arms depot in Bidgeneh, 21 miles to the west of the Iranian capital Tehran, state-owned Press TV reported.
At least 15 soldiers were killed and several others wounded, according to local reports cited by Reuters. Some of those injured remain in critical condition, said military spokesperson Ramazan Sharif.
The blast, which Agence France Presse said could be heard up to 25 miles away, was initally reported to have occurred in a gas-distribution station.
Officials later told the ISNA news agency that the explosion had instead hit an Revolutionary Guards base being used to store ammunition.
The depot "caught fire by accident," according to local lawmaker Hossein Garrousi. No further details have been given.
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A rescue helicopter, several ambulances and search dogs have been sent to the scene by police and the Red Crescent, Ynet News cites Tehran Police Chief Ahmad-Reza Radan as saying.
The explosion shattered windows in houses in Tehran's western suburbs, witnesses told AFP.
The sound of it was "deafening," a resident of nearby Karaj city told the BBC.
A crisis committee has been set up to investigate, Garrousi told the semi-official Fars news agency.
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The incident follows speculation that Israel and the US were planning strikes against Iranian nuclear facilities, which a UN report recently said had been used to work on weapon technology.
Tehran has warned it will retaliate to any attacks.