German police have opened an investigation into the possible poisoning of two Russians living in exile, officials said on Sunday.

Russian investigative media outlet Agentstvo reported that two Russian dissidents who attended a meeting in Berlin on April 29 and 30 described feeling ill. The meeting was organized by Kremlin critic and exiled oligarch Mikhail Khodorkovsky.

Berlin police officials told news agencies that they were looking into the case. They provided no other details saying the probe was ongoing.

What do we know about the two Russians?

One is a journalist who recently left Russia. The journalist experienced unspecified symptoms during the course of the event but said the symptoms may have also shown prior to the summit. She was treated at the Charite Hospital in east Berlin.

This journalist later published a Telegram post, where she said she did not get sick during or after the Khodorkovsky forum. The journalist said in the post that "one cannot say for sure that it is poisoning," while adding she is being treated diligently by the doctors at the Charite. 

The second participant is Natalia Arno, the director of Free Russia Foundation in the US. The foundation is an international organization that supports civil society in Russia. Arno has been in the US for a decade now.

Arno wrote on her Facebook that she thought she was jet lagged and tired when she felt unwell in Berlin. She then traveled to Prague, where she said she found her hotel room door ajar. She said she suffered sharp pain and strange symptoms.

Multiple Kremlin critics have accused the government of poisoning them, including opposition leader Alexei Navalny and journalist Vladimir Kara-Murza. Since the start of the Ukraine war, a string of Russian businessman and politicians have also died in mysterious ways. 

While the Kremlin has denied any involvement in suppressing critics, European countries and the US have slapped sanctions against Russia's intelligence agency, the Federal Security Service or the FSB, for leading the charge in poisoning Navalny with a nerve agent in 2020.

rm/dj (Reuters, AP)  

This article was later amended after a Telegram post from one of the exiled Russians disputed being ill in connection with the Khodorkovsky conference