Divisions between the groups fighting to topple Iraq's Prime Minister Nouri al-Maliki are emerging.

Much of the attention from the current insurgency has focused on ISIS - the Islamic State in Iraq and the Levant, but it is only one of a number of militia groups fighting.

Former General Muzhir al Qaisi is a spokesman for the General Military Council of the Iraqi Revolutionaries, which entered Mosul alongside ISIS and is taking part in the campaign. He told the BBC's Middle East correspondent Jim Muir that Mosul was too big a city for ISIS to have taken alone.

He also stressed the differences between the two groups, describing ISIS as "barbarians".