Attacks on hospitals since Syria's war broke out have left more than 700 doctors and medical workers dead, many of them in air strikes, UN investigators said Tuesday (June 21st).

The UN Commission of Inquiry on Syria also condemned horrific violations by extremists and voiced concern that extremist groups may have recruited hundreds of children, AFP reported.

Commission chief Paulo Pinheiro told the UN Human Rights Council that widespread, targeted aerial attacks on hospitals and clinics across Syria "have resulted in scores of civilian deaths, including much-needed medical workers".

"More than 700 doctors and medical personnel have been killed in attacks on hospitals since the beginning of the conflict," he said.

Pinheiro also denounced attacks on civilian infrastructure such as markets, schools and bakeries.

"With each attack, terrorised survivors are left more vulnerable," he said.

Pinheiro said the commission was investigating allegations that al-Nusra Front (ANF) "and other al-Qaeda-affiliated groups have recruited hundreds of children under 15 in Idlib".

He also condemned violations committed by the "Islamic State of Iraq and the Levant" (ISIL).

Syria's conflict is preventing millions of children from attending school, and activists have warned this is helping fuel extremist recruitment drives.