This image provided by Shaam News Network, which has been authenticated based on its contents and other AP reporting, purports to show dead bodies after an attack on Ghouta, Syria on Wednesday, Aug. 21, 2013. | Uncredited/AP

BERLIN — Russia says it has compiled a 100-page report detailing what it says is evidence that Syrian rebels, not forces loyal to President Bashar Assad, were behind a deadly sarin gas attack in an Aleppo suburb earlier this year.

In a statement posted on the Russian Foreign Ministry’s website late Wednesday. Russia said the report had been delivered to the United Nations in July and includes detailed scientific analysis of samples that Russian technicians collected at the site of the alleged attack, Khan al Asal.

Russia said its investigation of the March 19 incident was conducted under strict protocols established by the Organization for the Prohibition of Chemical Weapons, the international agency that governs adherence to treaties prohibiting the use of chemical weapons. It said samples that Russian technicians had collected had been sent to OPCW-certified laboratories in Russia.

The report itself was not released. But the statement drew a pointed comparison between what it said was the scientific detail of the report and the far shorter intelligence summaries that the United States, Britain and France have released to justify their assertion that the Syrian government launched chemical weapons against Damascus suburbs on Aug. 21. The longest of those summaries, by the French, ran nine pages. Each relies primarily on circumstantial evidence to make its case, and they disagree with one another on some details, including the number of people who died in the attack.

The Russian statement warned the United States and its allies not to conduct a military strike against Syria until the United Nations had completed a similarly detailed scientific study into the Aug. 21 attack. It warned that what it called the current “hysteria” about a possible military strike in the West was similar to the false claims and poor intelligence that preceded the United States invasion of Iraq.

“The Russian report is specific,” the ministry statement said. “It is a scientific and technical document.”

The statement also noted that the attention paid to the Aug. 21 attack had diverted attention from the investigation into the March 19 incident, which was the reason U.N. investigators were in Syria when the more recent attack took place.

“Unfortunately, that investigation still essentially has not begun,” the statement said.

There was no immediate comment from the United States. Independent chemical weapons experts contacted by McClatchy said they had not had time to read the Russian document, which was released as Secretary of State John Kerry was appearing before the House Foreign Affairs Committee to make the Obama administration’s case for a retaliatory strike on Syria as punishment for the attack.

A U.N. team spent four days late last month investigating the Aug. 21 incident. The samples it collected from the site and alleged victims of the attack are currently being examined at OPCW labs in Europe. U.N. Secretary General Ban ki-Moon has urged the United States to delay any strike until after the results of that investigation are known.

Richard Guthrie, formerly project leader of the Chemical and Biological Warfare Project of the Stockholm International Peace Research Institute, who said he had not seen the original report, said the Russian statement on the makeup of the sarin found outside Aleppo, which the Russians said indicated it was not military grade, might reflect only that “there are a lot of different ways to make sarin.”

He added: “The messy mix described by the Russians might also be the result of an old sarin stock being used. Sarin degrades (the molecules break up) over time and this would explain a dirty mix.”

But he also said that there could be doubts about the Russian conclusion that the rockets that delivered the sarin in the March 19 incident were not likely to have come from Syrian military stocks because of the use of RDX, an explosive that is also known as hexogen and T4.

“Militaries don’t tend to use it because it’s too expensive,” Guthrie said. He added in a later email, however, that it’s not inconceivable that the Syrian military would use RDX “iff the government side was developing a semi-improvised short-range rocket” and “if there happened to be a stock available.”

“While I would agree that it would be unlikely for a traditional, well-planned short-range rocket development programme to use RDX in that role, it is not beyond the realms of possibility that, as the Syrian government did not seem to have an earlier short-range rocket programme, it may have been developing rockets with some haste and so using materials that are at hand,” he said.

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