More than 700 doctors and medical workers have been killed in attacks on hospitals since the war in Syria broke out five years ago, a U.N. investigator said Tuesday.

Paulo Pinheiro, head of the U.N. commission of inquiry on Syria, revealed the tally in remarks at a session of the U.N. Human Rights Council in Geneva.

With the deterioration of medical conditions, the mortality rate of children and pregnant women has been on the rise in Syria, he said.

The war in Syria broke out in March 2011, leaving more than 280,000 people dead and forcing half the population to flee their homes.

Attacks on hospitals are a major problem in Syria. Recently, Doctors Without Borders, known by its French acronym MSF, evacuated medics and patients from northern Syria as Islamic State militants neared.