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 insistence by the Russian government that Navalny wasn�t necessarily poisoned � comments amplified by Russian doctors and pro-Kremlin media � 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 outrage from Navalny�s allies, who say 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 launching 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 before such a proble..

�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 Putin�s fiercest critics, fell ill on a flight back to Moscow from Siberia on Thursday and was taken to a hospital in the city of Omsk after the plane made an emergency landing.

Over the weekend, he was transferred to the Charit� hospital in Berlin, where doctors on Monday said they have 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.

U.S. Secretary of State Mike Pompeo said that if reports about Navalny�s poisoning �prove accurate, the United States supports the EU�s call for a comprehensive investigation and stands ready to assist in that effort.�

In response to statements from European officials, the speaker of the State Duma, Russia�s lower parliament house, charged Tuesday that Navalny�s condition could have resulted from a Western plot.

Duma speaker Vyacheslav Volodin in tasked 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.

Charit� said Monday that Navalny had undergone extensive examination by a team of physicians and that �clinical findings indicate poisoning with a substance from the group of cholinesterase inhibitors.�

That covers a broad range of substances that are found in several drugs, but also in pesticides and nerve agents. Charit� said the specific substance to which Navalny was exposed isn�t yet known but that a further series of comprehensive tests had been started.

The suggestion that Navalny was poisoned has been vehemently rejected in Russia, where a number of Kremlin critics fell victims to suspected poisonings in recent years, since last week. Government officials, medical specialists and state-controlled media offered a variety of possible explanations for Navalny�s condition.

Doctors in Omsk, a city in Siberia where Navalny was first hospitalized, ruled out poisoning as a diagnosis 24 hours after the politician was admitted and said �a metabolic disorder� was a likely diagnosis.

The editor-in-chief of the RT state-funded TV channel, Margarita Simonyan, speculated that the politician must have suffered from a sharp drop in blood sugar. Some pro-Kremlin news outlets alleged that Navalny mixed moonshine with sleeping pills.

The Charit� statement on Monday prompted another array of denials.

The chief intensivist with Russia�s Heath Ministry, Igor Molchanov, questioned whether detecting �substances affecting cholinesterase� five days after Navalny fell ill was at all possible.

Doctors in Omsk said they tested the politician for cholinesterase inhibitors and didn�t find any.

Peskov said Tuesday that specialists in Omsk noted �lowered levels of cholinesterase� � an obstruction of cholinesterase enzymes can be detected by blood tests, experts say � in his body in a matter of �hours� after he was brought in, but that it could have been triggered by a number of causes, including by �taking various medications.�

Navalny�s spokeswoman, Kira Yarmysh, on Tuesday said the government�s reluctance to launch an investigation was expected.

�It was obvious that the crime would not be properly investigated and a culprit found. However, we all know perfectly well who that is,� Yarmysh tweeted.

Western experts have cautioned that it is far too early to draw any conclusions about how the agent may have entered Navalny�s system, but note that Novichok, the Soviet-era nerve agent used to poison former Russian spy Sergei Skripal and his daughter in Britain, was a cholinesterase inhibitor.

�Cholinesterase inhibitor poisons can be given in many ways, they can be transported in many forms, and are very potent,� said Dr. Richard Parsons, a senior lecturer in biochemical toxicology at King�s College London. �This is why they are a favored method of poisoning people.�

Dr. Thomas Hartung, of the Johns Hopkins Bloomberg School of Public Health in Maryland, said such substances are easy to detect, even days and weeks after the poisoning, and that �we will know soon which substance was used.�

�The Novichok nerve agents, used in the 2018 poisoning of the Russian double agent Skripal in England, also belong to this category of substance,� he said. �I said at the time that the Russians could have have just left a business card at the crime scene, because the substances can be so clearly traced.�

(AP)