Russian opposition leader Alexei Navalny, who the West says was poisoned allegedly with a Novichok nerve agent, is regaining mobility and able to leave his bed, the Berlin hospital treating him said on Monday.

The improvement in his condition came as two European laboratories corroborated the findings that the Soviet-era military grade nerve agent was used on the Kremlin critic, prompting French President Emmanuel Macron to demand President Vladimir Putin to shed light on the “attempted murder”.

Hitting back at doubts raised by Russia about the German investigation, Chancellor Angela Merkel’s spokesman Steffen Seibert said Berlin had asked France and Sweden “for an independent review of the German evidence on the basis of new samples from Navalny”.

“The results of this review at specialised laboratories in France and Sweden are now available and confirm the German evidence” of the use of the banned weapons-grade substance,” Seibert said.

The results prompted Macron to tell the Russian president in telephone talks that it was “imperative that all light be shed, without delay, on the circumstances of this attempted murder and who is responsible”, the French presidency said in a statement.

Putin fired back that the claims remained “unsubstantiated accusations based on nothing against the Russian side”.

In an interview with the RTVI television network on Monday, Russian foreign minister Sergei Lavrov accused the West of going “beyond all the limits of decency and reasonableness”.

“Our Western partners look at us arrogantly, but we too have the right to doubt their claims of professionalism,” he said.

Germany was still waiting for the outcome of a separate evaluation by the OPCW global chemical weapons watchdog, Seibert said.