The United States strongly condemned an alleged chemical weapons attack in Syria’s Eastern Ghouta late Saturday, saying Russia bore some responsibility due to its “unwavering support” for the regime.

Douma, the last opposition holdout in Eastern Ghouta, was pounded by renewed airstrikes that killed 70 civilians in around 24 hours – while 11 people also suffered breathing problems.

First responders have accused forces loyal to President Bashar al-Assad of using poisonous chlorine gas. “The Assad regime and its backers must be held accountable and any further attacks prevented immediately,” US State Department spokesperson Heather Nauert said in a statement.

“Russia, with its unwavering support for the regime, ultimately bears responsibility for these brutal attacks.”

Nauert repeated the US’s previous assertions that Moscow had “breached its commitments to the United Nations as a framework guarantor” and questioned the Kremlin’s commitment to ending the crisis.

“Russia’s protection of the Assad regime and failure to stop the use of chemical weapons in Syria calls into question its commitment to resolving the overall crisis and to larger non-proliferation priorities,” she said, calling upon Moscow to join international efforts to prevent further attacks.

The Syrian regime has been repeatedly accused of using chemical weapons, with the United Nations among those blaming government forces for a deadly sarin gas attack on the opposition-held village of Khan Sheikhun in April 2017.

Since February 18, the regime’s Ghouta offensive has killed more than 1,600 civilians.