IS leader urges Mosul fighters

An Islamic State leader has urged fighters in Iraq's city of Mosul to turn "blood into rivers".

Islamic State leader Abu Bakr al-Baghdadi has urged his fighters in an audio recording posted online not to retreat from the northern Iraqi city of Mosul, but also to invade Turkey and attack Saudi Arabia.

Al-Baghdadi called on his militants to transform into rivers the blood of the Iraqi forces attempting to retake Mosul in Nineveh province.

"Do not retreat ... this whole war only gives us more faith to fight towards victory which is a promise from God," al-Baghdadi said in the video, posted on Thursday.

"To all the strugglers and the people of Nineveh, beware of any weakness ... fight and struggle and face your enemy," he added.

He called on the suicide bombers "to confront the enemy and transform their blood into rivers ... transform their days into dark nights."

"This war is your war," he said.

Islamic State overran Mosul in mid-2014 at the beginning of a lightning offensive that saw it seize swathes of Sunni Arab northern and western Iraq.

On October 17, government forces, Kurdish troops and Sunni and Shiite fighters, backed by US-led airpower, started a long-awaited campaign to liberate Mosul, Islamic State's de facto capital in Iraq.

The Islamic State leader fiercely criticised Turkey.

"The fighters of the Caliphate, here comes the atheist, Turkish soldiers ... show them your strength," Al-Baghdadi said in the 31-minute audio recording posted on the Islamic State website al-Furqan.

Turkey has been backing opposition rebels fighting Islamic State in northern Syria.

The recording could not be independently verified by dpa.

US State Department spokesman Mark Toner said that while US had not made a final determination, it didn't have "any reason to doubt" the tape's authenticity.