The Kremlin has said it will ignore demands from western countries to release jailed opposition activist Alexei Navalny, and suggested that his call for supporters to protest against his incarceration was illegal.

The US, UK and EU have condemned Mr Navalny’s detention and demanded he be released, while three EU member states called on the bloc to impose new sanctions against Moscow amid growing fears of a crackdown against opposition figures ahead of September’s parliamentary elections.

“We hear these statements but we cannot and will not take them into account,” Dmitry Peskov, the spokesman of President Vladimir Putin, told reporters on Tuesday, in the Kremlin’s first response to the jailing. “We are talking about the fact of a violation of Russian law by a Russian citizen. It is a completely internal affair, and we will not allow anyone to interfere. We have no intention of listening to these statements.”

Mr Navalny, Mr Putin’s most vocal critic, was sent to prison on Monday a day after returning to Russia, ahead of a court hearing next month that could see him jailed for three and a half years.

He was detained at passport control on Sunday night after arriving from Germany, where he had been recovering from an attempted assassination using the Soviet-developed nerve agent novichok. The Kremlin has denied allegations from western governments that it was responsible for the poisoning.

Mr Peskov described claims that Mr Putin was afraid of Mr Navalny as “absolute nonsense”, and said his treatment by Russia’s judicial system “cannot be associated with the president”.

The anti-corruption campaigner and political organiser has been barred from running in presidential elections against Mr Putin, jailed a number of times for organising or participating in rallies against the president and subjected to a barrage of legal challenges from Kremlin-friendly businessmen.

He was sent to jail on Monday by a judge who presided over a makeshift hearing hastily set up in a police station on the outskirts of Moscow, described by Edgars Rinkevics, Latvia’s foreign minister, as a “kangaroo court”.

In a video message recorded from inside the courtroom, Mr Navalny called on his supporters to attend street protests on Saturday, saying it was what Russian authorities “fear the most”.

Mr Peskov denied the Kremlin was fearful of such rallies but described Mr Navalny’s call as “alarming”.

In comments that suggest the authorities may seek to prevent such protests from taking place, Mr Peskov said that while the Kremlin was not the correct body to judge, Mr Navalny’s encouragement of protests could be seen as “something illegal”.

Mr Navalny was taken to Moscow’s infamous Matrosskaya Tishina prison on Monday evening, and is being held alone for 14 days due to Covid-19 quarantine rules, Russian prison ombudsman Alexey Melnikov wrote in a Facebook post.