Russia on Sunday accused Germany of stalling efforts to probe opposition politician Alexei Navalny's case after Berlin demanded Moscow provide an explanation over his poisoning or face sanctions.

Russian foreign ministry spokeswoman Maria Zakharova accused German authorities of failing to respond to a request by Russian prosecutors sent on August 27. She spoke after German Foreign Minister Heiko Maas said Russia must soon provide an explanation over Navalny's poisoning with Novichok, a banned nerve agent developed in the Soviet Union.

"Dear Mr Maas, if the German government is sincere in its statements then it should be interested in preparing a response to a request of the Russian Prosecutor General's Office as soon as possible," Zakharova said.

"So far we are not certain that Germany is not playing a double game," she added. "Where is the 'urgency' you are insisting upon?

"By not sending its answer, Berlin is stalling the process of investigation for which it's calling. On purpose?"

Germany, the current head of the European Union, will discuss possible sanctions on Russia over the poisoning of Russian President Vladimir Putin's top foe if the Kremlin does not provide an explanation soon, Maas said Sunday.