In a statement today, it says the violence has resulted in massive displacement in and around the city, with some 80,000 children now internally displaced and living in temporary shelters and camps.
US-backed Syrian forces launched their attack on Raqqa earlier this week and US-led coalition airstrikes have intensified.
"An estimated 40,000 children remain trapped in extremely dangerous conditions in Raqqa. Many are caught in the crossfire," said UNICEF regional director Geert Cappelaere.