Video from Kurdish Rudaw TV showed explosions and exchanges of gunfire occurring along the main road linking the northern city to Kirkuk.

Iraqi special forces entered Mosul earlier this month, gaining a foothold on the city's eastern edges as they seek to reclaim the city from ISIS.

However, the advance slowed as they pushed into more densely populated neighbourhoods.

The urban landscape inside Mosul proper makes defence easier for the militants, who are eager to hold on to the last major Iraqi stronghold of their self-styled caliphate.

Defeat in Mosul would be a major blow to their project, and they have said they are ready to fight to the death

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