MOSCOW -- The Kremlin brushed off allegations Tuesday that Russian opposition leader Alexei Navalny was the victim of an intentional poisoning orchestrated by authorities and said there were no grounds for a criminal investigation so far since it hasn't been fully established what caused the politician to fall into a coma.
The Russian government's insistence that Navalny wasn't necessarily the victim of a deliberate poisoning -- comments amplified by Russian doctors and pro-Kremlin media outlets-- came a day after doctors at a German hospital where the 44-year-old is being treated said tests indicated he was poisoned.
Moscow's dismissals elicited anger from Navalny's allies, who claim the Kremlin was behind the illness of its most prominent critic.
Kremlin spokesman Dmitry Peskov said the accusations against the government "absolutely cannot be true and are rather an empty noise."
"We do not intend to take it seriously," Peskov said.
Peskov said he saw no grounds for opening a criminal investigation at this stage, saying that Navalny's condition could have been triggered by a variety of causes and determining what it was should come first.
"If a substance [that caused the condition] is found, and if it is determined that it is poisoning, then there will be a reason for an investigation," Peskov said.
Navalny, a politician and corruption investigator who is one of Russian President Vladimir Putin's fiercest critics, fell ill on a flight back to Moscow from Siberia on Thursday and was taken to a hospital in the Siberian city of Omsk after the plane made an emergency landing.
Over the weekend, he was transferred to the Charite hospital in Berlin, where doctors on Monday said they found indications of "cholinesterase inhibitors" in his system.
These act by blocking the breakdown of a key chemical in the body, acetycholine, that transmits signals between nerve cells. Navalny is being treated with the antidote atropine.
Navalny's wife, Yulia Navalnaya, has been visiting her husband daily and made no comment to reporters as she arrived Tuesday.
Chancellor Angela Merkel personally offered Germany's help in treating Navalny and has called for a full Russian investigation -- a sentiment echoed Tuesday by officials from the United States, France and Norway.
Secretary of State Mike Pompeo said that if reports about Navalny's poisoning "prove accurate, the United States supports the [European Union's] call for a comprehensive investigation and stands ready to assist in that effort."
On Tuesday, Deputy Secretary of State Stephen Biegun met with Russian Foreign Minister Sergei Lavrov and other diplomats. He expressed deep concern about Navalny's condition, "the impact on Russian civil society of reports of his poisoning, and the importance of transparency and freedom of speech in any democratic society," the U.S. Embassy spokesperson, Rebecca Ross, said on Twitter.
After the meeting, the Russian Foreign Ministry said in a statement that Biegun warned Russian diplomats that if Navalny's poisoning is confirmed, the U.S. could take steps that will exceed Washington's response to evidence of Russia's meddling in the 2016 U.S. presidential election.
In response to Western statements, the speaker of Russia's lower parliament house claimed Tuesday that Navalny's condition could have resulted from a Western plot.
State Duma speaker Vyacheslav Volodin authorized lawmakers to look into what happened to Navalny to make sure it wasn't "an attempt by foreign states to inflict harm on the health of a Russian citizen and create tension in Russia" in order to "come up with more accusations" against the country.
Information for this article was contributed by Angela Charlton and Vladimir Isachenkov of The Associated Press.