Iraqi government forces are advancing into Tikrit on several fronts, forcing Islamic State (IS) militants to fall back to the city centre, officials say.

Soldiers and militiamen have reportedly retaken areas and key sites in the north, south and west, including a police headquarters and a hospital.

The Shia militias leading the fight are taking heavy casualties, and say victory will take several more days.

Defence correspondent Jonathan Beale travelled to Tikrit with the Shia "Badr Brigade" militia.