Russian Opposition leader Alexei Navalny, who is recovering after being allegedly poisoned, on Thursday accused President Vladimir Putin of being behind the attack, AFP reported.

“I assert that Putin is behind this act, I don’t see any other explanation,” he told German websiteDer Spiegel. Navalny’s allies have maintained that the Opposition leader was deliberately poisoned, but Russian authorities have dismissed evidence on this.

The news website reported that Navalny’s health condition was better after he recovered from his coma earlier in September, adding that he seemed well as he was alert and joking during the interview. It, however, added that Navalny’s hands were shaking so much he could not drink water from a bottle properly. Navalny told the website that he was planning to return to Russia.

“My job now is to remain the guy who isn’t scared,” he was quoted as saying. “And I’m not scared.”

Navalny was first admitted to a hospital in the Siberian city of Omsk where doctors said they found no trace of poisoning, according to AP. He was shifted from Omsk to Berlin for medical treatment on August 22. Physicians overseeing Navalny’s health, however, said his condition was too unstable for him to be moved after the German specialists arrived on a plane with advanced equipment. Navalny’s supporters alleged it was a ploy of the Russian government to delay the politician’s transfer so that the poison would not be traceable.

On September 2, German Chancellor Angela Merkel said that the Russian opposition leader was poisoned with a Soviet-style Novichok chemical nerve agent. The findings were corroborated by labs of France and Sweden. Novichok, a potent class of chemical weapon developed by the Soviet Union, is the same substance used on former spy Sergei Skripal and his daughter in England in 2018.

Germany, which holds the presidency of the European Union, had warned Russia of sanctions if it did not thoroughly investigate the poisoning case. Russia denied the allegations and accused Western countries of launching a disinformation campaign against it.

Last year, Navalny, serving jail time, was taken from a prison to a hospital, due to the suspected poisoning. At the time, doctors said he had a severe allergic attack and discharged him from the hospital the next day. In 2017, Navalny was attacked by several men who threw antiseptic in his eyes, damaging one eye.

Navalny had campaigned to run against Putin in the 2018 presidential elections, but was barred from contesting. Navalny’s Foundation for Fighting Corruption has been exposing graft among high-level government officials. However, last month, Navalny had to shut down the organisation after Yevgeny Prigozin, a businessman with close ties to the Kremlin, filed a lawsuit against him.