Iran's semi-official Tasnim news agency is reporting that four members of the Iranian Special Forces were killed in Syria while fighting against the Islamic State group.

The Tasnim news agency, which is considered close to the Iran's powerful Revolutionary Guard, reported the deaths but did not elaborate on the circumstances.

A number of Iranian soldiers have been killed in Syria, including high-ranking officers.

Iran is a key ally of Assad and has provided military and financial support throughout the five-year civil war.