Russian police have asked Germany to allow officers to question opposition politician Alexei Navalny, who is undergoing treatment in Berlin after being allegedly poisoned with nerve agent, Novichok.
The high profile Kremlin critic and anti-corruption activist, 44, who was hospitalised in Siberia after falling ill on a flight to Moscow in August, was transferred to a hospital in the German capital.
German doctors treating Navalny said there was "unequivocal evidence" that the politician had been poisoned by a nerve agent similar to Novichok, something Russia denies.
Novichok is a nerve agent developed by Soviet scientists during the Cold War and subsequently banned under the 1997 Chemical Weapons Convention.
Navalny has since been taken out of an induced coma and was responsive, his doctors said on Monday.
Russian transport police, who have started "preliminary" inquiries into the "hospitalisation of Navalny," said that they were preparing a request for its officers to shadow German investigators.
In a statement, Russia said its police officers could "ask clarifying and additional questions" and be present as "German colleagues carry out investigative activities with Navalny, medics and experts" now that Navalny's condition had improved.
On Wednesday, the Russian Foreign Ministry invited German Ambassador Geza Andreas von Geyr to protest what it called “unfounded accusations and ultimatums" against Russia put forward by the German government. It charged that Berlin has used the Navalny case ”as a pretext to discredit our country on the global arena."
Russia unsuccessfully demanded that German authorities provide its own investigators with data that led them to conclude “without doubt” that Navalny was poisoned with the Soviet-era nerve agent, including all biological materials and the results of samples and tests.
Germany said the data had been provided to the Hague-based Organization for the Prohibition of Chemical Weapons, of which Russia is a member.
“This international organisation, of which Russia is also a member, has a treaty-based mandate to oversee and enforce the ban on the use, production, storage as well as research into chemical weapons," Arne Collatz, a spokesman for Germany’s Defense Ministry, told reporters in Berlin.