As many as 50 people, including 12 children, have been killed in missile attacks on three separate hospitals in northern Syria.

Activists have accused Russia of carrying out the attacks, and Russian military aircraft have been in action in the skies near the hospitals.

Moscow has not commented on the strikes and continues to claim that it only targets “terrorists” in Syria, but the majority of Russian air strikes have been on more moderate rebel groups with no links to Islamic State or Jabhat al-Nusra, al-Qaeda’s affiliate in Syria.

The UN has condemned the attack, which it said were “a blatant violation of international laws”.

One of the attacks was on a Medecins Sans Frontieres (MSF) clinic in Maarat al-Numan, which the aid group said “appears to be a deliberate attack on a health structure”. The MSF facility was struck with four missiles within minutes and left seven people dead.

A separate attack targeted a second hospital in Maarat al-Numan, which is in Idlib province, killing three people.

A children’s hospital and two schools were the target of a third attack in Azaz, near the Turkish border. Aid workers in the area have blamed Russia for the attack, which killed at least 12 children.

Seventeen hospitals have been targeted by air strikes in the last six weeks.