"The regime attacked yet another hospital, and 20 people were killed and 100 people were wounded," Kerry said ahead of a meeting with his French counterpart, citing recent attacks. "Russia and the (Syrian) regime owe the world more than an explanation about why they keep hitting hospitals and medical facilities and children and women."
He added, "These are acts that beg for an appropriate investigation of war crimes. And those who commit these would, and should, be held accountable for these actions."
French Foreign Minister Jean-Marc Ayrault joined Kerry in his condemnation, saying the conflict has reached a "moment of truth" for the UN Security Council, and dismissing the Syrian regime's assertion that it is targeting terrorists in the besieged city of Aleppo, a stronghold of opposition forces fighting the Assad regime.
"These are indeed war crimes," Ayrault told reporters Friday .
"Bombing access to clean water is not against terrorism," he said. "When you bomb a hospital it is the same. We need a ceasefire as soon as possible."
Kerry has been increasingly harsh in his criticism of the Russian government in recent weeks for its intervention in Syria, where Moscow is backing President Bashar al-Assad in the brutal, five-year-long civil war.
Last month, after a brief US and Russian-backed ceasefire agreement fell apart and airstrikes resumed, the secretary of state delivered a blistering address to the UN Security Council, accusing the Assad regime of targeting civilians and Russia of targeting a UN aid convoy.
"How can people go sit at a table with a regime that bombs hospitals and drops chlorine gas again and again and again and again and again and acts with impunity?" Kerry asked at the time.
"You're supposed to sit there and have happy talk in Geneva while the regime drops bombs?"
On Friday, Kerry said attacks on medical professionals in Syria are "way beyond" accidental.
"This is a targeted strategy to terrorize civilians and to kill anybody and everybody who is in the way of their military objectives," he said.
Ayrault said he plans to travel to New York ahead of a UN Security Council meeting Saturday, where the French are expected to put forward a resolution that will call for a ceasefire in Aleppo, including a halt to Syrian and Russian air attacks.
Russia is expected to veto the measure, but says it is willing to support a separate UN proposal to escort rebel fighters from the al-Nusra terrorist group out of Aleppo.