Russian opposition leader Alexei Navalny posted a picture of himself from his hospital bed in Germany on Tuesday, looking gaunt but joking wryly about his condition and saying that he was enjoying the ability to finally breathe on his own after being poisoned with a nerve agent.

The Instagram post was the first image of the 44-year-old released since he was taken to Berlin's Charite hospital two days after falling ill on a domestic flight in Russia on Aug. 20.

"Hi, this is Navalny," he wrote in the Russian-language post. "I have been missing you. I still can't do almost anything on my own, but yesterday I managed to breathe on my own for the entire day."

Navalny had been kept in an induced coma for more than two weeks as he was treated with an antidote before hospital officials said on Sept. 7 that his condition had improved enough for him to be brought out of it.

On Monday, the hospital said he had been removed from mechanical ventilation and was able to leave his bed for "short periods of time."

In the photo, Navalny is being given a hug by his wife Yulia and is flanked by his two children as he sits upright in his bed in a hospital gown. His statement even had the ring of his well-known sarcastic humor.

"Just on my own, no extra help, I didn't even use the simplest valve in my throat," he said of being able to breathe without ventilation. "I liked it very much. It’s a remarkable process that is underestimated by many. Strongly recommended."

Despite his recovery, doctors have said they cannot rule out long-term health issues associated with the poisoning.

Navalny’s spokeswoman, Kira Yarmysh, tweeted that once he had recovered, Navalny plans to return to Russia.

"No other option has ever been considered," she wrote.

Leonid Volkov, a top associate of Navalny, refused to give any details on his condition or his possible return when reached by The Associated Press (AP) on Tuesday.

A German military lab has determined that Navalny was poisoned with Novichok, the same class of Soviet-era agent that Britain said was used on former Russian spy Sergei Skripal and his daughter in Salisbury, England, in 2018. On Monday, the German government said independent tests by labs in France and Sweden backed up its findings.

French President Emmanuel Macron’s office said he had expressed "deep concern over the criminal act" that targeted Navalny directly with Russian President Vladimir Putin on Monday. The Kremlin said Putin in the call "underlined the impropriety of unfounded accusations against the Russian side" and emphasized Russia’s demand for Germany to hand over analyses and samples.

Kremlin spokesman Dmitry Peskov told reporters Tuesday that Russia is puzzled by the German refusal to share Navalny's analyses and other medical data or compare notes with the Russian doctors who found no trace of poison in his system while he was at a hospital in the Siberian city of Omsk.

"Russia has been absolutely open for cooperation in determining what happened," Peskov said. "Russia needs cooperation with the German side in getting the patient's biological samples to be able to advance."

Russian Foreign Minister Sergey Lavrov, who has canceled a scheduled trip Tuesday to Berlin, said Russian authorities have conducted a preliminary inquiry and documented the meetings Navalny had before falling ill, but he emphasized the need to see the evidence of his poisoning to launch a full criminal investigation.

Lavrov charged that Navalny’s life was saved by the pilots of the plane who quickly landed in the Siberian city of Omsk when he collapsed on board and by the rapid action of doctors there. He accused the West of trying to smear Russia and use the incident as a pretext for new sanctions against Moscow.

Berlin has rejected suggestions from Moscow that it is dragging its heels on sharing evidence.

With Germany’s findings corroborated by labs abroad, "we do not expect the bringer of the bad news – namely us – to be attacked further, but rather that they should deal with the news itself," German Foreign Minister Heiko Maas said on Monday of Russian authorities.

Asked why no samples from Navalny have been given to Russia, his spokeswoman noted that "Mr. Navalny was in Russian treatment in a hospital for 48 hours."

Most of Germany’s political parties have joined Merkel in calling for an investigation, but leaders in the far-right Alternative for Germany, known for its pro-Russian sympathies, have said Berlin should not be involved. On Tuesday it invited media to a discussion with a Russian parliamentarian on "the Russian view of the Navalny case."