The UN’s aid chief has asked Russia to explain how it uses data on the location of Syrian hospitals and clinics following a string of attacks on health facilities.

Mark Lowcock, the under-secretary-general for humanitarian affairs, told the Security Council he was “not sure” hospitals that share coordinates of their location under a UN de-confliction system will be protected.

More than 23 hospitals have been hit by attacks since Russia-backed Syrian forces launched an offensive in the rebel-controlled Idlib region in late April, according to the UN.

On June 20, an ambulance transporting a wounded woman in southern Idlib was hit, killing the woman and three medical workers.

“I have written to the Russian Federation to request information as to how the details provided through the de-confliction mechanism are used,” Lowcock told the council.

Russia, which backs Syrian forces in their offensive in the northwest, has firmly denied that the bombing campaign has targeted hospitals in the rebel-controlled Idlib region.

Moscow maintains the military operation is aimed at driving out “terrorists” from the region, which is covered by a de-escalation agreement reached last year between Russia, Iran and Turkey.

Hay’et Tahrir al-Sham (HTS), Syria’s former al-Qaeda affiliate that is on the UN terrorism list, controls most of Idlib province as well as parts of neighbouring Aleppo, Hama and Latakia provinces.

The war in Syria, now in its ninth year, has killed hundreds of thousands of people and displaced millions since it started with the repression of anti-government protests in March 2011.