Activists and medical staff said at least 21 people were killed on Wednesday in a Syrian regime blitz over war-ravaged eastern Aleppo that pounded hospitals, a blood bank and targets near schools. Four children were among the dead. With nine barrel bombs striking the Children's Hospital, Al-Bayan Hospital and the Central Blood Bank, staff on site with the Syrian American Medical Association told CNN, the Al-Shaar neighborhood appeared to be the worst hit. Buildings nearby were completely flattened. The activist group Aleppo Media Center said, at least 50 others have been wounded. Children's Hospital Director Dr. Hatem said there were closer to 20 barrel bombs dropped on the facility. As the bombardment continued, he said its staff was hunkering down in the basement.