A representative of Iraq's most senior Shi'ite cleric, Grand Ayatollah Ali al-Sistani has urged people to take up arms and defend their country.
The call came as ISIS Islamist fighters vowed to march to Baghdad after seizing control of a number of towns and cities across Iraq.
Sheikh Abdulmehdi al-Karbalai was delivering the sermon at Friday prayers in the city of Kerbala.
The Foreign Secretary has been clear on the threat of Isis, but he has ruled out the prospect of any UK military involvement in the crisis.
Iraq’s foreign minister, Hoshyar Zebari, is a natural diplomat. Polite, immaculately dressed, and blessed with a great memory.
Isis has paraded military equipment in Mosul it captured from when the Iraqi army fled in what some see as a "nightmare scenario."