The Russian military has a history of issuing pre-emptive statements accusing anti-government forces of laying the groundwork for so-called “false flag” operations to invite U.S. airstrikes. President Vladimir Putin rejected Syria’s involvement in a deadly, suspected chemical attack in 2017, and Russia again dismissed another suspected poison gas attack in April 2018 as “ staged .”

The Russian military has warned that the United States is helping Syrian rebels stage a chemical weapons attack against civilians, which it claims will be used as cover to carry out airstrikes against government targets.

In a statement carried by Interfax on Monday, the Russian Defense Ministry claimed that the anti-government Free Syrian Army rebels had brought chlorine canisters to the eastern province of Deir ez-Zor. The goal, according to the ministry, was that videos of the aftermath would be used to “justify” U.S. airstrikes and a rebel offensive.

“The Russian Defense Ministry warns that using these provocations to destabilize the situation in Syria is unacceptable,” said spokesman Major General Igor Konashenkov.

Members of the Organization for the Prohibition of Chemical Weapons (OPCW) have warned of an increased use of chemical weapons, particularly in Syria. Some expressed frustration at OPCW’s inability to lay blame when attacks were carried out with banned munitions.

Reuters contributed reporting to this article.