Iraq Shia militias isolate IS-held Mosul from Syria's Raqqa

Forces battling the Islamic State group [IS] in northern Iraq cut off the jihadists' last supply line from Mosul to Syria on Wednesday, trapping them in the city for a bloody last stand.

A day after the last major bridge over the Tigris in Mosul was bombed by the US-led coalition against IS, elite forces fighting in the east of the city also reported significant progress.

To the west of Mosul, Hashd al-Shaabi (Popular Mobilisation Units [PMU]) paramilitary forces made a push to cut the road between two towns on the route heading to Syria.

"PMU forces have cut off the Tal Afar-Sinjar road," senior militia commander Abu Mahdi al-Mohandis said on social media.

Iraqi military commander Dhiya al-Gharbawi told The New Arab that additional federal forces have been sent to support the PMU in the assault on Tal Afar, which lies about 50 kilometres west of Mosul and is still under the control of the jihadists.

"The PMU are stationed on the outskirts of the city and will very soon begin storming the town," Gharbawi said.

	The US-led coalition destroyed Mosul's "third bridge" [Twitter]

The push by the PMU - a paramilitary umbrella group dominated by Tehran-backed Shia militias - has been vital to cut off IS escape routes, however, its involvement around Sunni-majority Mosul and its targeting of Tal Afar have proved deeply divisive.

Alleged executions and abuses carried out by fighters in towns and villages taken from IS elsewhere have stoked local fears.

The latest development will make it very long and dangerous for IS if it attempts to move fighters and equipment between Mosul and the Syrian city of Raqqa, the last two bastions of their crumbling "state".

On Tuesday, the US-led coalition that has carried out thousands of air raids against IS targets in Iraq and Syria since August 2014 said it destroyed a key bridge in Mosul.

The last bridge still standing in Mosul is from the British era and not big enough for heavy vehicles to move across the Tigris, which runs through the middle of the city.

The IS aligned Amaq news agency released video footage of Mosul's "third bridge" after the attack, revealing the destruction.

The number of civilians displaced since last month's start of the offensive against Mosul has risen to 68,000, but most of the city's population remained trapped.