Berlin (dpa) - Germany is looking to its allies to forge a joint response after it found "unequivocal" evidence of a nerve agent attack on Russian dissident Alexei Navalny, who is being treated in an intensive care unit in Berlin.

The head of the German parliament's committee for foreign affairs, Norbert Roettgen, called for Europe to take a clear, tough and unified line on the issue.

"Now we have again been brutally confronted with the inhuman reality of [Russian President Vladimir] Putin's regime," he told the ARD public broadcaster late Wednesday.

He was speaking hours after the German government announced that Navalny had been the victim of an attack, citing the results of a toxicology test carried out by the Bundeswehr military that found traces of a chemical nerve agent from the Novichok group in Navalny's system.

The 44-year-old protest leader, one of Putin's fiercest opponents during the past decade, was flown to Berlin for treatment on August 22, two days after he fell ill on a domestic flight in Russia.

Merkel condemned the attack, saying it aimed "to silence him," and German Foreign Minister Heiko Maas summoned Russian ambassador Sergei Nechayev in protest, calling for a full and transparent investigation.

Merkel had previously said that there could be a joint response similar to the coordinated action taken following the 2018 Novichok poisoning of former Russian double agent Sergei Skripal in Britain, when 30 Western allies expelled Russian diplomats.

In reaction to the new findings, Putin's spokesperson Dmitry Peskov said Russian authorities are ready to fully cooperate with Germany with regards to Navalny.