The foreign ministry in Moscow said it had summoned German ambassador Geza Andreas von Geyr and protested "unfounded accusations and ultimatums against Russia" and the "obvious use of (Navalny's) situation by Berlin as a pretext to discredit our country".
It again urged Berlin to respond to a request from Russian prosecutors for the evidence, including medical data, that led Germany to declare that Navalny, one of President Vladimir Putin's fiercest critics, had been poisoned with nerve agent Novichok.
Failure to provide the materials will be seen as a "gross hostile provocation" that would be "fraught with consequences for Russian-German relations, as well as a serious complication of the international situation," the ministry said.
Navalny, a 44-year-old lawyer and anti-corruption campaigner, suddenly fell seriously ill last month as he took a flight in Siberia and was evacuated to Berlin for treatment.
US Secretary of State Mike Pompeo charged Wednesday that "there is a substantial chance that this actually came from senior Russian officials."
He warned that the United States would also investigate the poisoning and may take its own action.
"It's something that we'll take a look at, we'll evaluate, and we'll make sure we do our part to do whatever we can to reduce the risk that things like this happen again," he said in a radio interview.
'Massive disinformation campaign'
Moscow went on a diplomatic offensive on Thursday over the case, hitting back at Western accusations and talk of new sanctions against Russia.
As well as summoning the German envoy, the foreign ministry issued a response to a G7 statement calling for those behind the suspected poisoning to be quickly found and prosecuted.
The ministry denounced an "ongoing massive disinformation campaign" aimed at "mobilising sanctions sentiment" that had nothing to do with Navalny's health or "finding out the genuine reasons for his hospitalisation".
"Unfounded attacks on Russia are continuing," the ministry said, with a "whipping up of hysteria" around the case.
Germany said last week there was unequivocal evidence that Navalny had been poisoned with Novichok, the same substance used in the 2018 attack on a former Russian double agent and his daughter in the English city of Salisbury.
Navalny's associates say the use of Novichok, a military-grade nerve agent, shows that only the Russian state could be responsible, but the Kremlin strenuously denies any involvement.
Russian officials have repeatedly accused Germany of being slow to share the findings of its investigation despite the request from prosecutors.
The Navalny poisoning is the latest in a long series of assassination attempts against Kremlin critics.
Already suffering from wide-ranging Western sanctions imposed over its 2014 annexation of Crimea, as well as the effects of the coronavirus pandemic and the drop in oil prices, Moscow is anxious to avoid any further pressure on its economy.
As well as talk of sanctions, some in Germany have called for an end to the Nord Stream 2 project, a 10 billion euro ($11 billion) pipeline beneath the Baltic Sea that is near completion and set to double Russian natural gas shipments to Germany.
Navalny became sick after boarding a plane in Siberia last month, with aides saying they suspect he drank a cup of spiked tea at the airport.
He was initially treated at a local hospital, where doctors said they were unable to find any toxic substances in his blood, before he was flown to Berlin for specialised treatment.
The hospital treating him said Monday that he was out of a medically induced coma and reacting to speech.