Russia has "done little" to establish truth over the poisoning of opposition figure Alexey Navalny, leaving an impression that it is not interested in it, German Foreign Minister Heiko Maas told RIA Novosti in an interview.

"We do not see the Russian government publicly analyzing the circumstances of the case on the merits. And the circumstances are such that a military nerve agent from the Novichok group was used on the territory of Russia, which is a serious violation of the Chemical Weapons Convention," Maas said.

According to the minister, many members of the international community demand that Russia shed light on the circumstances of the incident.

"So far, Russia has done little to clarify them. And when new and partly absurd theories are being constantly put forward, including claims that Navalny poisoned himself, when the reputation of the OPCW [the Organisation for the Prohibition of Chemical Weapons] as an independent organization is being called into question, all this only reinforces the impression that there is no real interest in clarifying the circumstances of what happened," the minister argued.

Meanwhile, it is only up to Russian law enforcement agencies to investigate the alleged attack on Navalny, as it happened on Russian soil, the diplomat went on.

"All traces, witnesses and evidence necessary for the investigation, as well as the first blood samples are in Russia. Alexey Navalny was taken to Germany for treatment two days after the assassination attempt," Maas stated.

The Russian prosecution launched a preliminary investigation into the incident with Navalny on 20 August, the very day when he fell ill aboard a Russian domestic flight, prompting a plane emergency landing in Siberia.

Russian doctors, however, found no toxic substances in the 44-year-old's system. Later, he was transported for treatment to Germany, which soon claimed to have evidence of his poisoning with a nerve agent from the Novichok group. The OPCW confirmed last week that a substance similar to nerve agent Novichok, but not included on the lists of banned chemicals, had been found in Navalny's system.

Moscow insists that Berlin present the biological materials to corroborate the chemical poisoning, so that it could open a criminal case. According to Russian authorities, they have already sent four requests for legal assistance to Berlin, but to no avail.