Russia's attorney general has submitted a request to German authorities for judicial assistance with regards to the suspected poisoning of Russian opposition leader Alexei Navalny, the Berlin-based Welt am Sonntag reported on Sunday.

The newspaper said Germany's Justice Ministry had confirmed receipt of the request, in which Moscow asked for analysis and preliminary medical diagnoses to be sent.

Russian authorities suggested that a preliminary probe into the incident has yet to produce evidence of criminal activity. However, Russian media reports said that the investigation would likely be extended until September 20.

The Russian hospital that treated Navalny before his transfer to Germany said he likely fell ill as a result of low blood sugar.

Read more: Was Alexei Navalny poisoned with Novichok?

Likely poisoning

However, German doctors at the Berlin Charite hospital said earlier this week that clinical findings "indicate poisoning with a substance from the group of cholinesterase inhibitors."

That group includes Novichok, which British authorities believe was used to poison Russian double-agent Sergei Skripal in 2018.

"Mr. Navalny continues to be treated in an intensive care unit, where he is being kept in a medically-induced coma and on a ventilator," said the Charite hospital. "Due to the severity of the patient's poisoning, it remains too early to gauge potential longterm effects."

Previous attempt

This is not the first time that Navalny has been targeted by a suspected poisoning plot. Last year, Navalny was hospitalized after coming into contact with a "toxic agent," according to his personal physician.

Navalny is a leading Russian opposition figure and former presidential candidate who has openly criticized Russian President Vladimir Putin. His supporters have suggested that Russia's security apparatus are implicated in the poisoning since they routinely monitor the opposition figure.

ls/mm (AFP, dpa)