Russia has dismissed a United Nation report on the August 21 sarin gas attack in Damascus as "biased and one-sided" and says it has Syrian-supplied evidence that shows rebels were responsible.

The Russian deputy foreign minister, Sergei Ryabkov, said on Wednesday that his country was disappointed with the UN report published this week, calling it "distorted and one-sided".

"We are disappointed, to put it mildly, about the approach taken by the UN secretariat and the UN inspectors, who

prepared the report selectively and incompletely," he said after talks with President Bashar al-Assad in Damascus.

Ryabkov said the regime had given Russia material implicating rebel groups in the August 21 attack, and later stated on Russian television that it was "given to Mr [Ake] Sellstrom who headed the group of UN inspectors" but that it did not "receive adequate attention in the report."

Sergey Lavrov, the Russian foreign minister, said the regime's evidence would be presented to the UN.

The UN report, released on Monday, did not ascribe blame but detailed munitions and rockets used in the August 21 attack, their likely point of origin and their capacity. One missile used could hold 56 litres of sarin gas. As little as 0.5mg of sarin can kill an adult.

The US holds Assad responsible for the August 21 attack, which it says killed 1,429 people. The regime denies responsibility and its ally Russia maintains that there is no evidence implicating Assad.

The UN later said its conclusions were beyond questioning. "The findings in that report are indisputable," UN spokesman Martin Nesirky said. "They speak for themselves and this was a thoroughly objective report on that specific incident."

Meanwhile, the Human Rights Watch (HRW) group released its analysis of the UN report,saying that it showed two of the missiles fired on August 21 originated from a Republican Guard compound.

"Connecting the dots provided by these numbers allows us to see for ourselves where the rockets were likely launched from and who was responsible," Josh Lyons, a satellite imagery analyst for HRW, said.

Hower, the evidence was "not conclusive", he said.

Ryabkov is on a visit to Damascus to present the Syrian regime with the results of the agreement between Russia and the US reached in Geneva, Switzerland, to rid Syria of its chemical weapons.

He said he emphasised to Muallem the importance of the Syrian side "strictly and swiftly" handing over details of its chemical weapons arsenal to the Organisation for the Prohibition of Chemical Weapons, the first step in the agreement.

The Russia-US agreement is aimed at warding off the threat of US-led military action as retribution for the chemical attack.

Ryabkov said he assured the Syrian side that there was "no basis" for a UN Security Council resolution on the chemical weapons agreement to invoke Chapter VII of the UN Charter that allowed the use of force and tough sanctions.

He said this could only be considered if the UNSC was able to confirm violations of the convention on chemical weapons. "This is a hypothetical situation."