MOSCOW (Reuters) – Pyotr Verzilov, an anti-Kremlin activist treated at a Berlin hospital for suspected poisoning, was given a police guard for his own protection, a close friend who visited him in hospital said on Tuesday.

Verzilov, editor of a Russian online news portal closely linked to punk protest group Pussy Riot, suddenly fell ill two weeks ago, losing his sight, hearing and the ability to walk.

German doctors have found no trace of the poison in his body although they say there is no other explanation for his condition. Verzilov, in a tweet from the hospital on Tuesday, said he had been struck by “wonderful poisons … something new and surprising.”

Hunter Heaney, a close friend who visited Verzilov at the Charity Hospital in Berlin, said he noticed he was followed by two strangers near his home and near the hospital.

He was concerned for his safety and called the German police. Police responded by taking Verzilov, his family members and Heaney into police custody for their protection.

“We are most definitely under police protection all the time,” he told Reuters by phone from Berlin.

A spokesperson for the Berlin police said they were in contact with Verzilov and his entourage and the situation was constantly being assessed. “We ask you to understand that we are not commenting on possible measures in detail,” the spokesperson said.

Nadezhda Tolokonnikova, a member of Pussy Riot who was previously in a relationship with Verzilov and has a child from their relationship, visited her in Berlin and only returned to Moscow on Sunday.

She told Reuters in Moscow his condition had improved and he could be released from the hospital in a few days. She said, however, that he was still suffering from episodes of delirium and his pupils had dilated.

Nika Nikulshina, with whom Verzilov is currently in a relationship, told Reuters: “The forecast is good although Petya (Verzilov) is not yet stable.”

Earlier, a Berlin doctor said that Verzilov was probably poisoned because there was no other explanation as to why Verzilov was in such a state. However, no official evidence of poisoning was found in her body, according to Tolokonnikova.

Verzilov was one of four Pussy Riot activists who ran onto the pitch during the FIFA World Cup final in Moscow in July to protest police brutality. When he fell ill, he was treated in a Russian hospital for four days before being flown to Berlin for further treatment.

Tolokonnikova said Russian doctors concluded that he was not poisoned and diagnosed him with psychological problems. She said that despite this diagnosis, doctors pumped her stomach and performed liver dialysis.

In a Twitter post on Tuesday, Verzilov said, “I’ve only been relatively conscious for only three days, and before that it was like being in a black hole.”

He added, “I spend my days in the friendly company of wonderful poisons. But not polonium 210 or Novichok, but something new and surprising.

Polonium is the radioactive isotope that poisoned former Russian spy Alexander Litvinenko in London in 2006. He later died and British police claimed he was the victim of a Russian state sponsored plot, an allegation denied by Moscow.

British officials have identified Novichok, a nerve agent developed by the Soviet Union, as the substance that poisoned former Russian double agent Sergei Skripal and his daughter last year. They survived. The Russian denied any involvement.