An Iranian news agency report says there has been an explosion in the city of Isfahan.
A noise said to sound like a blast was heard but Iranian security forces have not confirmed its source. An important Iranian nuclear facility is located near the city.
Satellite photos just released by the US apparently show the destruction from another blast that happened less than three weeks ago at a military base.
Seventeen Revolutionary Guards, including the head of the elite force’s missile programme, were killed. Iran says the explosion was caused by an accident while weapons were being moved.
Monday’s suspected blast has attracted much attention as the West and Israel closely monitor Iran’s nuclear programme.
There has been media speculation in Israel that its secret service agents are involved in suspected attacks in Iran.