Gunmen shot dead a member of Iran's Revolutionary Guards on Sunday in the east of the capital Tehran, state news agency IRNA reported.

"Sayyad Khodai... was assassinated during a gun attack carried out by two motorcylists in Tehran's Mohahedin-e Eslam Street," IRNA said.

The agency described him as a "defender of the sanctuary" -- a term used to describe anyone who works on behalf of the Islamic republic in Syria or Iraq.

The Islamic Revolutionary Guards Corps, the ideological arm of Iran's military, identified Khodai as a colonel. 

In a statement posted on their website, the Guards also denounced a "terrorist act" they claimed was carried out by "elements linked to global arrogance" -- a reference to the United States and its allies.

The Guards said they launched an investigation to identify the "aggressor or aggressors".

According to IRNA, Khodai was killed by five bullets as he returned home at around 4:00 pm (1130 GMT).

The agency published pictures showing a man slumped over in the driver's seat of a car, with blood around the collar of his blue shirt and on his right upper arm.

He is strapped in with his seat belt and the front window on the passenger side has been shot out.