Mosul campaign: Iraqi troops closing in slowly on ISIS-held western half of city
Video report by ITV News correspondent Angus Walker
Iraqi forces are closing in around western Mosul as they seek to recapture the northern city from so-called Islamic State.
Iraq's prime minister, Haider al-Abadi, announced the offensive early on Sunday and as the day progressed troops were reported to be within striking distance of Mosul airport.
The campaign to re-take Mosul began last year, but until this recent announcement there had been a lull in the fighting.
Renad Mansour, an Iraq analyst with the think tank Chatham House, told ITV News the announcement was unusual, given that the Mosul operation had been active for months, but that it was likely made to boost the counter-terror forces' spirits.
"Very clearly it's about morale," he said.
The Iraqi forces have already seized several small villages south of the city, according to statements from the armed forces joint command.
Islamic State militants were forced out of the eastern part of the city earlier in the campaign and are now essentially under siege in the western half of the city, along with an estimated 650,000 civilians.
The Mosul campaign for the western half of the city will be hard fought.
"Mosul would be a tough fight for any army in the world," the commander of the US-led coalition forces, Lt Gen Stephen Townsend, said in a statement.
To date, the coalition has conducted more than 10,000 air strikes against Islamic State targets in Iraq.
It has also trained and equipped more than 70,000 Iraqi forces, the statement said.
Speaking to journalists in the UAE, James Mattis, the US defense secretary, declined to give details about US battle plans.
Islamic State has escalated its insurgency in retaliation for the military setbacks that have, over the past year, forced it out of most Iraqi cities it had captured in 2014 and 2015.
Two militants blew themselves up in eastern Mosul on Sunday, killing three soldiers and two civilians, and wounding a dozen people, Reuters reported security sources as saying.