Iran has supplied Iraq with attack jets to help it counter an offensive by Sunni rebels led by the Islamist group Isis, strong evidence suggests, BBC News reported.

Russia supplied an initial delivery of the aircraft just a few days ago.

But analysts at the International Institute for Strategic Studies (IISS) in London say that a further delivery, on 1 July, originates from Iran. This means that the U.S. - which has also sent aircraft to Iraq - is operating alongside Iran in this conflict.

The U.S. has deployed drones and helicopters to Iraq and is actively gathering intelligence on the advance by the Islamic State in Iraq and the Levant (Isis). Washington is also supplying Iraq's existing air force with Hellfire missiles.