The Assad regime and its Iranian-backed militia allies targeted a school and a hospital, along with other civilian settlements in the Idlib de-escalation zone in Syria, killing nine civilians, including at least three children, and injuring 12 others, local sources said Wednesday.

The regime targeted civilian settlements in Jisr al-Shughur, Saraqib, Ariha districts and some villages, including Rub Al Cuz, Bseidah and Merdih with airstrikes and ground attacks beginning in the early hours of Wednesday, Syrian Civil Defense White Helmets said.

Regime forces also targeted a school in the Ariha district and a hospital in Jisr al-Shughur, sources said.

The full casualty count from the attacks on the school and the hospital remain unclear, as research and rescue work is continuing in the area.

More than 540 civilians have been killed in regime and Russian airstrikes in northwestern Syria since the end of April, according to the Syrian Observatory for Human Rights.

The United Nations says 25 health facilities in the region have been hit.

As the opposition's last enclave, Idlib's prewar population of 1.5 million has swelled to around 3 million with new refugee waves after it was designated a de-escalation zone under the Astana agreement between Turkey, Russia and Iran in May 2017 to pave the way for a permanent political solution in Syria.

Turkey and Russia inked a deal for a buffer zone in September in Sochi to prevent a massive regime offensive on the Idlib region, near the Turkish border.

Following eight months of calm provided by the Sochi deal, the Assad regime intensified its attacks starting April 26 under the pretext of fighting the Hayat Tahrir al-Sham (HTS) terrorist group holed up in Idlib.

The intermittent attacks and bombardments have killed, wounded or displaced thousands. Residential areas have been destroyed by indiscriminate attacks, while numerous educational facilities, health facilities and residential areas have collapsed or have become unusable after being targeted by bombs.