UNITED NATIONS—Russia on Monday lashed out at the U.S. and its allies on the U.N. Security Council over who is to blame for chemical weapons attacks in Syria this year.

Russia’s ambassador told the council that the dramatic Aug. 21 attack that led to Syria agreeing to give up its chemical stockpile was “staged” and a “large-scale provocation.”

Vitaly Churkin compared it to the “manipulation of public opinion” that led up to the U.S. invasion of Iraq. He read reporters the statement he read to council members.

The current council president, French Ambassador Gerard Araud, told reporters only that members had an “acrimonious exchange.”

The spirited session came as the council received its first briefing from Secretary-General Ban Ki-moon on the final report of a U.N. inspection team that last week said chemical weapons probably were used in Syria several times.

The team did not have the mandate to say whether the Syrian government or opposition fighters were responsible for the attacks.

Russia is Syria’s most powerful ally, and it has used its veto power in the council in the past to block actions against the regime of President Bashar Assad.

The British ambassador to the U.N., Mark Lyall Grant, tweeted after Monday’s session, “Russia uses Giant Squid Defence – squirt lots of ink in attempt to muddy waters on regime culpability. Doesn’t work.”

Churkin did not explicitly mention the United States in his accusation over the Aug. 21 chemical attack in Ghouta, in which the U.S. government said more than 1,400 people were killed.

But Syrian Ambassador Bashar Ja’afari said of the U.S. and its efforts to prepare all sides for peace talks next month in Geneva, “You cannot be an arsonist and a fireman at the same time.”

Ban on Monday again demanded that those responsible for the chemical weapons attacks be held accountable.

He told the council that it has a “primary role in bringing perpetrators to justice” because it repeatedly has said the use of weapons of mass destruction is a serious threat to international security.

But how that would happen is not clear. Araud said the issue was not discussed at Monday morning’s session.

The U.N. inspection team concluded that chemical weapons were probably used in four locations in Syria, in addition to the confirmed use of the deadly nerve agent sarin in Ghouta, near Damascus, in August.

Chief inspector Ake Sellstrom last week said “more intrusive methods” than those authorized for his investigation are needed to pinpoint the perpetrators.

“I could speculate … but I don’t have information that will stand up in court,” he said.

A commission created by the U.N. Human Rights Council has already determined that both sides have committed heinous war crimes during the Syrian conflict. The Geneva-based commission is producing a confidential list of suspected criminals.