German doctors treating Russian opposition leader Alexei Navalny have contacted Bulgarian colleagues amid suspicions he was poisoned with the same mysterious toxin used on an arms dealer.
'Obviously, they consider it possible that the same or very similar substances were used,' reported news magazine Der Spiegel.
Doctors at Berlin's Charité hospital - where Navalny remains in a coma - said they believe the 44-year-old Vladimir Putin critic was poisoned with an unknown substance used variously in drugs, insecticides and nerve agents.
In 2015, Bulgarian doctors found that arms dealer Emilian Grebev was poisoned but were unable to identify the substance.
This came as Navalny's wife, Yulia, 44, who is at his bedside in Berlin, marked their 20th wedding anniversary by quoting the words of a song: 'Our power in is our love. Don't give up, live!'
'Sometimes you can afford to be a little sentimental. Today is exactly that kind of day,' posted Yulia the anniversary date of the anniversary on Wednesday.
She also posted a video showing the defiant Putin foe walking out of prison, and with their children.
The words of the song she chose for her 'Don't give up - live' message are from Russian singer Anna Sedokova.
Yulia was flooded with messages wishing her strength and her husband a full recovery.
The couple's daughter Daria, 19, posted from the US where she is studying: 'Love is when you support each other in the court room. When you are ready to go through every challenge together for the sake of each other. Thank you for teaching me how to love, parents. Happy anniversary!'
The couple also have a son Zakhar, 12.
The Grebev case was seen as similar to the poisoning of Russian turncoat spy Sergei Skripal who was poisoned after a GRU hit squad was dispatched from Moscow, according to the British authorities.
Eight apparent Russian military intelligence officers travelled to and from Bulgaria in the weeks before and after Gebrev's poisoning, it is believed.
The contact between the German doctors and Bulgaria came as Russia today launched a probe into the hospitalisation of Navalny in Omsk last week.
His plane made an emergency landing after he was taken seriously ill, apparently after having drunk tea at Tomsk airport before catching a flight back to Moscow.
Russia has so far denied there is evidence that Navalny was poisoned.
Police have investigated his hotel room in Tomsk, and places he visited including the airport, and carried out checks on CCTV cameras.
'More than 100 items were seized that may have evidentiary value,' said a statement.
'More than 20 different forensic investigations - forensic, biological, physical and chemical - are being carried out.
'At the moment, no potent or narcotic substances have been found.'
But a woman who was with Navalny in Tomsk claimed Russia was mounting only a halfhearted probe into the suspected poisoning.
'They remembered about me finally, and today they questioned me,' said Ksenia Fadeeva, Navalny's candidate in the Tomsk city elections.
She was quizzed by transport police not the Russian Investigative Committee which is the equivalent of the FBI.
'I was interviewed by the senior lieutenant of the transport police. Why them? She herself does not know.
'She also doesn't know why the Investigative Committee is not doing this.'
Fadeeva said: 'I have a complete feeling that the security forces only create the appearance of work, and even this somehow they do very sluggishly.'
This article has been adapted from its original source.
© Associated Newspapers Ltd.