Peskov said President Vladimir Putin has been told about Navalny's death.
RUSSIA'S INVESTIGATIVE COMMITTEE
The committee said it has launched a procedural probe into the death.
NAVALNY AIDE LEONID VOLKOV, ON X
Volkov said he was unable to confirm the death, adding Navalny's lawyer was travelling to the site of the prison where the opposition leader had been serving his sentence.
NAVALNY'S DEPUTY, IVAN ZHDANOV, ON X
Said relatives of Navalny should be notified of his death within 24 hours, but no notifications have been made.
RUSSIAN NEWSPAPER EDITOR AND NOBEL PEACE PRIZE LAUREATE DMITRY MURATOV
Speaking to Reuters, Muratov called the death "murder" and said that he believed prison conditions had led to Navalny's demise.
BRITISH PRIME MINISTER RISHI SUNAK, ON X
"This is terrible news. As the fiercest advocate for Russian democracy, Alexei Navalny demonstrated incredible courage throughout his life."
FRENCH FOREIGN MINISTER STEPHANE SEJOURNE, ON X
"Alexei Navalny paid with his life for his resistance to a system of oppression. His death in a penal colony reminds us of the reality of Vladimir Putin's regime. To his family, his loved ones and the Russian people, France presents its condolences."
SWEDISH FOREIGN MINISTER TOBIAS BILLSTRÖM, ON X
"Dreadful news about Alexei Navalny... If the report about his death in Russian prison is true it represents another terrible crime by Putin's regime. The ruthlessness against Navalny shows again why it is necessary to continue to fight against authoritarianism."
EU COUNCIL PRESIDENT CHARLES MICHEL, ON X
"Alexei Navalny fought for the values of freedom and democracy. For his ideals, he made the ultimate sacrifice. The EU holds the Russian regime solely responsible for this tragic death."
NATO SECRETARY-GENERAL JENS STOLTENBERG
Said he was "deeply saddened and disturbed" by the reports of Navalny's death. "We need to establish all the facts, and Russia needs to answer all the serious questions about the circumstances of his death."
DUTCH PRIME MINISTER MARK RUTTE, ON X
Navalny's death "illustrates the unprecedented brutality of the Russian regime. Navalny fought for democratic values and against corruption. He had to pay for his struggle with death while he was held under the harshest and most inhumane conditions. I wish his family, loved ones and everyone who fought with him for change in Russia much strength."
BELGIAN PRIME MINISTER ALEXANDER DE CROO, ON X
"His tragic death again underscores why we will continue to support Ukraine. Russia will not prevail in Ukraine. Our thoughts are with the family and friends of Navalny and all brave Russian political prisoners."
LATVIAN PRESIDENT EDGARS RINKEVICS, ON X
"Whatever your thoughts about Alexei Navalny as the politician, he was just brutally murdered by the Kremlin. That's a fact and that is something one should know about the true nature of Russia's current regime. My condolences to the family and friends."
CZECH FOREIGN MINISTER JAN LIPAVSKY
"It's still the case that just as Russia treats its foreign policy, it treats its citizens. It has turned into a violent state that kills people who dream of a better future, like Nemtsov or now Navalny - imprisoned and tortured to death for standing up to Putin. Rest in peace."
