Iraqi forces have begun an operation to retake the western half of Mosul from the Islamic State group.
Prime Minister Haider al-Abadi announced the start of the operation early on Sunday morning on state television.
He said government forces were moving to "liberate the people of Mosul from Daesh oppression forever", using the Arabic acronym for IS.
South-west of Mosul, near the city's IS-held airport, plumes of smoke were seen rising into the sky as coalition aircraft bombed militant positions.
Further south at an Iraqi base, police forces were gathering and getting ready to move north.
Iraqi forces took control of eastern Mosul last month, but the west remains in the hands of entrenched extremists.
Mosul, Iraq's second-largest city, is roughly split in half by the Tigris River.
The battle for Mosul's western half is expected to be prolonged and difficult, due to the older, narrower streets.
Federal police forces moving in large numbers to villages south of western Mosul pic.twitter.com/6f5qkUENvI— Quentin Sommerville (@sommervillebbc) February 19, 2017