Reuters quoted US officials as saying that Russia or its loyalists were likely behind the leak of classified Pentagon documents containing partial details of the war in Ukraine.
Three U.S. officials said Moscow or pro-Moscow elements were likely behind the leak of several classified U.S. military documents on social media that included a partial glimpse of the war in Ukraine dating back a month.
U.S. officials said the documents appeared to have been modified to reduce the number of Russian troops killed and wounded, adding that their assessments were unofficial and not linked to an ongoing investigation into the leak itself.
The leaked documents outline Ukraine's combat capabilities, potential vulnerabilities, and NATO's extensive efforts to help Ukraine in Russia's war against it.
The documents from a month ago also contain U.S. national security secrets related to the Middle East and China.
For its part, the US Department of Justice announced in a statement the opening of an investigation into the matter, and the New York Times reported Thursday that the Pentagon is investigating how the documents were published.
The New York Times reported that a trove of documents believed to detail U.S. national security secrets had begun to appear on social media.
The newspaper, citing US officials, put the number of documents at more than 100. The newspaper's sources described the leak as a nightmare for the United States, Britain and Australia, as well as New Zealand and Canada, which share intelligence.
The newspaper quoted a former Pentagon official as saying that the leak appeared to be a deliberate act to damage the efforts of Ukraine, the United States and NATO.
In Ukraine's first official comment on the leaked Pentagon documents, Mykhailo Podolyak, an adviser to the Ukrainian president, said what she had addressed about Ukraine's preparations for a counterattack was fake and Russian disinformation.
Podolyak described the state of Russia's intelligence services as having deteriorated since the collapse of the Soviet Union to the point where they could only rehabilitate themselves with fake photo programs and dumps.
The adviser spoke of Moscow's attempt to disrupt Ukraine's counteroffensive and that it would reveal Kiev's plans on the ground.
No waiver of Crimea
Ukrainian President Volodymyr Zelensky said on Friday there was no alternative to returning Russian-occupied Crimea to Ukraine's control.
Zelenskiy said in a video message released by his office: "The world should know that respect and order will return to international relations only when the Ukrainian flag returns to Crimea."
In a separate video of his meeting with Muslim military personnel including representatives of the Crimean Tatars, Zelensky said: "Ending the occupation of Crimea is irreplaceable, not only for Ukraine, but for the world as a whole."
Crimean Tatars are an indigenous Muslim ethnic minority in Crimea, many of whom have fled the region for fear of political persecution while others are being held by Russia.
Zelenskiy's comments came after Brazilian President Luiz Inácio Lula da Silva proposed that Kiev cede Crimea, which Russia illegally annexed in 2014, as part of a peace deal with Moscow.
On the ground, local sources in the city of Donetsk reported that one person was killed and others wounded in shelling targeting the city in the Donbas region of eastern Ukraine.
Russian military sites said the Ukrainian shelling of a market in the city centre was carried out by Himars rocket launchers. The pro-Russian Donetsk authorities announced that 9 people were killed when Ukrainian forces shelled the city's Kalininsky district.
On the situation in Pakhmut, the British Ministry of Defense said in an intelligence assessment that Russian forces have recently regained momentum in the battle for control of the city, and are also seriously threatening the supply line of Ukrainian forces from the west.