An international medical relief organization says at least four of its staff have been killed in an air strike on a medical facility in Syria.
The Paris-based Union of Medical Care and Relief Organizations says the strike late on September 20 leveled a medical facility in the rebel-held town of Khan Touman, south of Aleppo.
The Britain-based Syrian Observatory for Human Rights said 13 people were killed, including four nurses and paramedics and nine rebel fighters, some of them belonging to Jabhat Fatah al-Sham -- formerly the Al-Qaeda-linked Al-Nusra Front.
The attack came a day after an attack on aid trucks and a warehouse that killed some 20 civilians on September 19, prompting the United Nations to suspend all humanitarian convoys in Syria.
The United States said it held Russia responsible for the attack.
Russia strongly denied involvement of its own or Syrian aircraft.