MOSCOW, September 2 (RIA Novosti) – The evidence the US has provided to Russia about use of chemical weapons by government forces in Syria is inconclusive, Russia’s Foreign Minister Sergei Lavrov said Monday.

US officials released a report Friday that presented what President Barack Obama called a “powerful case” that the Syrian government was behind an attack that killed hundreds of civilians in a Damascus suburb late last month. Syria claims militant rebel groups were responsible.

“We absolutely were not convinced by that [evidence] that our American partners, as well as the British and the French, showed us,” Lavrov said. “There are no facts, there’s only talk about what we know for certain. When we ask for more detailed evidence, they say, ‘You know, it’s all secret, so we can’t show you.’ That means that there are no such facts.”

The information the US provided lacked any concrete details, such as names or geographical coordinates that would prove its case, Lavrov said in a speech opening the new academic year at Moscow’s State Institute of International Relations (MGIMO). He did not specify if Friday's report by the US was the evidence to which he was referring.

When Russia asked for additional details from Western officials, he added, the request was denied.

Lavrov also criticized France and the UK for their “unreasonable” demands that the scope of a UN investigation into the attacks not be restricted to the location of the original incident.

“Great Britain and France said that sending inspectors to investigate this one concrete incident wouldn’t do. Let’s demand that [President Bashar] Assad agree to let in any number of inspectors with any equipment at any place and time, so that there’s not a single corner where the inspectors wouldn’t be able to go,” Lavrov said.

UN Secretary General Ban Ki-moon authorized a UN inspections team to investigate the first alleged attack, which took place on August 21 near Damascus.

The Syrian government then requested the team to also investigate three more purported chemical attacks it said were carried out by rebel groups, Syria’s ambassador to the UN told journalists last week.

The United States is considering carrying out armed intervention in Syria in response to the Assad regime’s alleged use of chemical weapons.

US Defense Secretary Chuck Hagel said August 25 President Obama had asked the US military to “prepare for all contingencies,” in response to the incidents US media reported. The United States Navy is building up its forces the eastern Mediterranean, including deploying destroyers armed with cruise missiles, US media said.

France is also considering use of armed force in Syria, but the UK ruled it out last Thursday after a surprise defeat for Prime Minister David Cameron in a parliamentary vote on the issue.