Hezbollah, an Iranian-backed Shi'ite Islamist group, has not previously announced any role in the conflict in Iraq, which escalated last month when radical Sunni militants seized large areas of territory from the Shi'ite-led government in Baghdad.
Four sources in Lebanon named the Hezbollah commander as Ibrahim al-Haj, a technical specialist involved in training. They said he was "martyred" in a battle near Mosul, a city in northern Iraq seized from government control last month by an al Qaeda offshoot known as the Islamic State.
ISIS vs Hezbollah? I wonder who gets martyred when they use suicide bombers against one another?