Russian President Vladimir Putin said on Tuesday he hoped a planned meeting of the global chemical weapons watchdog would help to defuse a major diplomatic row triggered by the poisoning of a former Russian double agent in England.
Britain has blamed Russia for the poisoning of Sergei Skripal and his daughter Yulia with a military-grade nerve agent in the English city of Salisbury on March 4. Moscow denies any involvement and has accused London of whipping up anti-Russian hysteria in the West.
The Skripal case has plunged East-West relations into their worst crisis since the Cold War, with Britain and its allies expelling around 130 Russian diplomats and Moscow responding with its own expulsions.
At Moscow's request, the Organisation for the Prohibition of Chemical Weapons (OPCW) will hold a special session on Wednesday in the Netherlands on the Salisbury poisoning.
"We have raised 20 questions for discussion (at the meeting). I hope that during this discussion a final line on what has happened will be drawn," Putin told a news conference during a visit to the Turkish capital Ankara.
Moscow has said it wants to take part in the official British investigation into the poisoning.
"We are interested in a full-fledged investigation. We want to be allowed into this investigation and we count on receiving relevant materials as the issue involves citizens of the Russian Federation," Putin said.
Earlier on Tuesday, the head of Britain's military research centre said it had so far been unable to tell whether the nerve agent, identified as Novichok, had been produced in Russia.
"I want to add that according to international experts' data there are around 20 countries capable of producing such neuro-paralytic substances," Putin said.
British counter-terrorism police say they believe Skripal, 66, and his 33-year-old daughter were poisoned with Novichok - an agent first developed by the Soviet military - that had been left on the front door of their home in Salisbury.
Putin, who won another six-year term in a presidential election last month, said he had learnt about the poisoning via the media and had been surprised by the pace of what he called an anti-Russian campaign unleashed by Britain.
Putin's spokesman, Dmitry Peskov, told reporters in Ankara that Britain's version of who was responsible for the poisoning "will not be confirmed anyway because it is impossible to confirm it".
"Indeed this is a long story, the insanity has gone too far," Peskov added.