Specialist labs in France and Sweden have confirmed Russian opposition leader Alexei Navalny was poisoned with the Soviet-era nerve agent Novichok, the German government said Monday.

A German military laboratory previously confirmed the substance in his samples.

German government spokesperson Steffen Seibert also said that the Hague-based Organization for the Prohibition of Chemical Weapons (OPCW) is taking steps to have samples from Navalny tested at its reference laboratories.

"Independently of the ongoing examinations by the OPCW, three laboratories have now confirmed independently of one another the proof of a nerve agent of the Novichok group as the cause of Mr. Navalny's poisoning,” Seibert said in a statement.

He said Germany had asked France and Sweden for an "independent review” of the German findings. German officials said labs in both countries, as well as the OPCW, took their own new samples.

Navalny, the most prominent opponent of Russian President Vladimir Putin, was flown to Germany two days after falling ill on Aug. 20 on a domestic flight in Russia and is being treated at Berlin's Charite hospital. Berlin has demanded that Russia investigate the case.

Seibert on Monday renewed Germany’s demand that "Russia explain itself” on the matter. He added that "we are in close consultation with our European partners on further steps.”

The Kremlin has bristled at calls from Chancellor Angela Merkel and other world leaders for Russia to answer questions in the case, denying any official involvement and accusing the West of trying to smear Moscow.

Russian authorities have prodded Germany to share the evidence that led it to conclude "without doubt” that Navalny was poisoned with a military nerve agent from the Novichok group, the same class of Soviet-era agent that British authorities said was used on former Russian spy Sergei Skripal and his daughter in Salisbury, England, in 2018. Berlin has rejected suggestions from Moscow that it is dragging its heels.

Seibert wouldn't identify the specialist French and Swedish labs at a regular government news conference. But the head of the Swedish Defence Research Agency, Asa Scott, told Swedish news agency TT: "We can confirm that we see the same results as the German laboratory, that is, that there is no doubt that it is about these substances.”

Asked why no samples have been given to Russia, German Foreign Ministry spokeswoman Maria Adebahr replied that "Mr. Navalny was in Russian treatment in a hospital for 48 hours.”

"There are samples from Mr. Navalny on the Russian side,” she added. "The Russian side is called on, even after three independent labs have established the result, to explain itself, and Russia has... all the information and all the samples it needs for an analysis.”

Navalny was kept in an induced coma for more than a week as he was treated with an antidote, before hospital officials said a week ago that his condition had improved enough for him to be brought out of it.

The Berlin hospital said Monday that Navalny "has been successfully removed from mechanical ventilation.” It added in a statement that "he is currently undergoing mobilization and is able to leave his bed for short periods of time.”