An explosion at a base belonging to Iran's Revolutionary Guards has killed 18 people and injured 14.
Reports are emerging of the blast at an ammunitions store on Tuesday in north-western Lorestan province.
The injured were taken to Khoramabad, 300 miles (500 km) southwest of Tehran.
An elite military force, the Revolutionary Guard was set up shortly after the 1979 Iranian revolution to defend the country's Islamic system.
It has since become a major military, political and economic force in Iran.
The Revolutionary Guard has been targeted by UN sanctions aimed at pressuring Iran to halt uranium enrichment.
The north-west of Iran has seen several attacks in recent months by Kurdish militants against the Iranian military.
The military is fighting armed groups and separatist movements in the south-east along the border with Pakistan as well as in the far north-west along the border with Iraq.
Tehran has accused the US and Britain of provoking ethnic unrest to undermine Iran's security
In October 2009, a suicide bomber killed at least 42 people, including senior Guard commanders, near the Pakistani border. Sunni rebels known as Jundallah, or Soldiers of God, were blamed.