Russia and Syria should be investigated for war crimes after carrying out a series of attacks on hospitals that left dozens of Syrian civilians dead, U.S. Secretary of State John Kerry said Friday.

Kerry said the latest attack from Syrian forces struck a hospital overnight, killing 20 people and wounding hundreds more. Those actions — plus the repeated airstrikes on hospitals and medical facilities — demand an explanation from both Russia and the Syrian regime, he said.

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"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," Kerry told reporters after welcoming French Foreign Minister Jean Marc Ayrault to Washington, D.C., on Friday.

Kerry’s remarks are the latest sign of the United States’ deteriorating relationship with Russia over the dire situation in Syria and other global crises. The U.S. cut all diplomatic ties with Russia and Syria earlier this week after finding they had not lived up to their end of the bargain to restore a ceasefire and allow for humanitarian aid to enter the region.

The U.S. accused Russia of orchestrating the airstrike on a United Nations humanitarian aid convoy last month that killed 20 people. Both Russia and Syria, however, deny involvement. The State Department also believes the two regimes played a role in attacks on two more hospitals and a bread distribution center last week.

“This is a targeted strategy to terrorize civilians and to kill anyone and everyone who is the way of their military objectives,” Kerry said Friday.