Iraqi special forces meanwhile pushed deeper into the city's eastern part, retaking the Falah neighbouring late yesterday, said Lt Gen Abdul-Wahab al-Saadi.
Fighting raged as a haze of fog and smoke hovered over the city, which was rocked by tank fire and airstrikes.
The children are among some 93,500 people who have fled since the operation began, while hundreds of thousands have remained in their homes. Mosul is Iraq's second largest city and the extremist group's last major urban stronghold in the country.
He said that once IS is driven from the city it will be important to "invest in children's services so this war doesn't continue."
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He could not provide an exact figure on how many children have been killed since the operation started, but he said some of them have been targeted by snipers.
"We know that children who have been queueing up for water have been targets," he said. "I saw a photograph of a child this morning who's been shot by a sniper queueing up for water."
"On day one they can't look you in the eye, they're not smiling, they're sad," he said. "But day after day when they start to draw, when they start to play with their friends... you see them start to smile, their eyes start to brighten up."
Mosul, about 360 kilometres northwest of Baghdad, fell to IS in the summer of 2014, when the group swept across northern and western Iraq.