An estimated 40,000 children are trapped in extremely dangerous conditions in Raqqa as fighting intensifies in and around the Syrian city, the United Nations Children's Fund (Unicef) has reported, warning that "many are caught in the crossfire."

The Unicef called on all parties to protect children inside Raqqa, provide safe passage to those wishing to leave the city and grant a protected environment to civilians who fled the city, reported Emirati news agency Wam, citing senior officials.

"Heavy violence in the city of Raqqa is threatening the lives of children," remarked Geert Cappelaere, Unicef regional director in the Middle East and North Africa (Mena) region, in a statement, which noted that at least 25 children were reportedly killed and scores injured in the city.

He explained that hospitals and schools have reportedly come under attack and that those attempting to flee are at danger of getting killed or injured.

He emphasised that children are being deprived of the most basic and life-saving necessities and that little aid have reached Raqqa since 2013 due to violence and access restrictions.

Cappelaere added that the conflict has resulted in massive displacements in and around the city, with some 80,000 children from Raqqa city now internally displaced and living in temporary shelters and camps.