Four aid workers killed in 'unacceptable' airstrikes near Aleppo

ALEPPO, Syria, Sept. 21 (UPI) -- At least four aid workers of the Union of Medical Care and Relief Organizations were killed Tuesday night by an airstrike that hit a medical center near Aleppo.

The aid organization said its workers died as they were rushing to pick up others who were injured in a separate attack in Khan Touman. Two nurses died, one nurse was critically injured and two ambulance drivers died. The aid organization said it was an "unacceptable" loss of life.

"They give their lives to save others," the organization said in a statement. "The instigators of these acts must be held responsible."

The Syrian Observatory for Human Rights said nine rebel militants were killed in Khan Touman airstrikes on Tuesday. It is not immediately clear which country launched the airstrikes.

The airstrikes follow a similar attack on a U.N. aid convoy that was struck as it attempted to deliver relief supplies to the besieged city of Aleppo. The Russian government denied that its military or that of Syrian President Bashar al-Assad were responsible for the attack that killed at least 20 people.

The United States said two Russian SU-24 fighter jets were in the sky above the aid convoy at the moment the airstrike occurred.

"There only could have been two entities responsible, either the Syrian regime or the Russian government," White House spokesman Ben Rhodes said Tuesday. "In any event, we hold the Russian government responsible for airstrikes in this space."