More than 2,000 fighters sent from Iraninfo-icon have been killed in Iraqinfo-icon and Syriainfo-icon, the head of Iran's veterans' affairs office said Tuesday.

"Some 2,100 martyrs have been martyred so far in Iraq or other places defending the holy mausoleums," Mohammad Ali Shahidi told the state-run IRNA news agency.

Shahidi, who is head of Iran's Foundation of Martyrs and Veterans Affairs, was speaking at a conference on martyrdom culture in Tehraninfo-icon.

The figure was more than double the number he gave in November, which referred only to Syria.

Iran is, with Russiainfo-icon, the main military backer of Syrian President Bashar al-Assad, and also organises militias fighting the militant Islamic Stateinfo-icon (IS) group in Iraq.

Shahidi did not provide details on the nationalities of those killed.

Iran oversees "volunteer" fighters recruited from among its own nationals as well as communities in neighbouring Afghanistaninfo-icon and Pakistaninfo-icon.

The families of those killed in battle are given Iranian citizenship under a law passed last May.

Tehran refers to the fighters as "defenders of the shrines" -- a reference to holy sites in Iraq and Syria that have been targeted by the militants.