NATO Secretary General Jens Stoltenberg expressed concern about the death of opposition leader Alexei Navalny in a penal colony, speaking with journalists at the Munich Security Conference on Friday.

"I am deeply saddened and concerned about reports coming from Russia that Alexei Navalny is dead. All the facts have to be established, and Russia has serious questions to answer," he claimed.

"Alexei Navalny has been a strong voice for freedom, for democracy for many years, and NATO, NATO allies have called for his immediate release for a long time, and today my thoughts go to his family and his loved ones, and we remain committed to support everyone that believes in democracy and freedom, as Alexei Navalny has done for so many years," continued the NATO secretary general.

Asked if there was any connection between Navalny's death and the upcoming presidential elections in Russia, Stoltenberg said: "I will not speculate today; I will just continue to call on Russia to make sure that all facts are established, that they answer all the questions that now will be asked, and then, based on that, we will be able to say more."

Alexei Navalny's death was reported by Russia's Federal Penitentiary Service on Friday. He was 47. The cause of death had not been released at time of publication.

Russian presidential spokesperson Dmitri Peskov said that the Federal Penitentiary Service was carrying out all 'inspections and inquiries' and refused to comment on speculation that the death could've been due to a 'thrombus detachment' - or blood clot.

US Secretary of State Antony Blinken claimed that 'Russia is responsible', while Ukrainian leader Volodymyr Zelensky alleged that it was 'obvious' that Vladimir Putin was behind the death. Neither provided any evidence to back their assertions.

Russian Foreign Ministry spokesperson Maria Zakharova said that "the instant reaction of NATO leaders to Navalny's death in the form of direct accusations against Russia is self-disclosing."

"There is no forensic examination yet, but the West already has conclusions ready," Zakharova added.

Navalny returned to Moscow in January 2021, after being treated in Germany for an alleged poisoning attempt while on a flight in Russia in August 2020.

He was initially detained at the airport in the Russian capital, and sentenced to two and a half years in jail for a parole violation stemming from a 2014 embezzlement conviction. The politician was subsequently charged with fraud and contempt of court, and given another nine years in prison.

Navalny claimed all accusations against him were politically motivated. In August 2023, he received another 19 years for inciting and financing extremism, among other charges.