The U.S. is urging the international community to demand that Syria not use chemical weapons any longer, following the sixth reported incident of chlorine gas use in the past 30 days.

“We implore the international community to speak with one voice, taking every opportunity to publicly pressure the Assad regime, and its supporters, to cease its use of chemical weapons and hold those responsible accountable for these brutal attacks,” State Department spokesperson Heather Nauert said in a statement.

The most recent attack impacted the Idlib Province near Saraqib, a northwestern city in Syria.

The statement issued Monday says that, “By shielding the Syrian regime from accountability, Russia has not lived up to its commitments. The use of chemical weapons by all parties in Syria must unequivocally stop. The people of Syria are suffering; the rest of the world is watching.”

Following one of the recent attacks last month, Secretary of State Rex Tillerson said that Russia, due to their support of Syrian President Bashar Assad, is responsible for the victims.

“Whoever conducted the attacks, Russia ultimately bears responsibility for the victims in East Ghouta and countless other Syrians targeted with chemical weapons since Russia became involved in Syria,” Tillerson said. “It has betrayed the Chemical Weapons Convention and UN Security Council Resolution 2218, and on these occasions has twice vetoed UN Security Council resolutions to enforce the Joint Investigative Mechanism and continue its mandate [to investigate attacks in Syria].”

Russia has used its United Nations Security Council veto to shield Assad from U.S. resolutions and other actions, including preventing the Joint Investigative Mechanism to probe allegations of chemical weapon use in Syria. Additionally, Moscow granted Assad military assistance against those attempting to remove him.

Earlier Monday, U.S. Ambassador to the U.N. Nikki Haley said it was a “true tragedy” that Russia has prevented the U.N. from condemning and launching an investigation into the use of chemical weapons.