The British government said late Friday it had summoned diplomats from the Russian embassy "to make clear that we hold the Russian authorities fully responsible" for the death of Russian opposition politician Alexei Navalny, a UK Foreign Office spokesperson confirmed.

Earlier, the Russian Federal Penitentiary Service announced the death of Navalny in a prison located in the Yamalo-Nenets Autonomous Area, adding that investigations are underway to determine the causes of his death.

British Foreign Secretary David Cameron had said that Russian President Vladimir Putin "should be accountable for what has happened."

Shortly after Navalny's death was announced by the Russian authorities, Western leaders rushed to point fingers at the Kremlin.

Kremlin spokesperson Dmitry Peskov on Friday labeled the remarks from Western politicians regarding Navalny's death as outrageous and unacceptable.

"The statements of Western countries are quite obvious. There is no medical statement, there is no information from forensic experts, there is no final information from the Federal Penitentiary Service, there is no information about the causes of death. And there are such statements. Obviously, they are absolutely outrageous. We consider such statements absolutely unacceptable," Peskov told reporters.

Navalny was a prominent Russian opposition politician who gained international recognition for his campaign on alleged corruption within the Russian government. On March 22, 2022, Navalny was found guilty of fraud and sentenced for ten years in prison. It was also revealed in November 2023 that he had collaborated with Western agencies to spread anti-Russian propaganda online.

UN chief Antonio Guterres also called for "a full, credible and transparent investigation" into Navalny's death.

US comments on Navalny's death another attempt to interfere in Russia's affairs: Antonov

In a related context, Russian Ambassador to Washington Anatoly Antonov said that US comments about the death of the Russian opposition figure are an interference in Russia's internal affairs and an attempt to use the situation to justify new sanctions.

"Make no mistake, Putin is responsible for Navalny's death," US President Joe Biden said in remarks from the White House shortly after Navalny's death. Similarly, US Vice President Kamala Harris said his death was a sign of what she called "Putin's brutality".

"The death of a person is always a tragedy. It is important in this situation to sort out all the details of what happened. However, local politicians do not want to wait and have already blamed the Russian authorities for everything... They are seeking a reason for... introducing additional sanctions... This is another attempt to interfere in the internal affairs of the Russian Federation," Antonov said.