Elon Musk said he refused to give Kyiv access to his Starlink satellite communications network over Crimea to avoid complicity in a "major act of war", reports BBC.
Kyiv had sent an urgent request to activate Starlink to Sevastopol, home to a major Russian navy port, Musk said.
He made the comments in response to allegations in a book that he had deactivated Starlink to prevent a drone attack on Russian ships.
A senior Ukrainian official claimed that this action facilitated Russian attacks and accused him of "committing evil".
Russian naval vessels had since been engaged in deadly attacks on civilians, he said.
"By not allowing Ukrainian drones to destroy part of the Russian military (!) fleet via Starlink interference, Elon Musk allowed this fleet to fire Kalibr missiles at Ukrainian cities," he said.
"Why do some people so desperately want to defend war criminals and their desire to commit murder? And do they now realize that they are committing evil and encouraging evil?" he added.
The row follows the release of a biography of the billionaire by Walter Isaacson which alleges that Musk deactivated Ukraine's access to Starlink out of concern that an ambush of Russia's naval fleet in Crimea could trigger a nuclear response from the Kremlin.
In an attempt to target Russian ships in Sevastopol, Ukraine deployed submarine drones loaded with explosives. However, the drones lost their connection to Starlink and "washed ashore harmlessly", Isaacson wrote.
Starlink terminals establish connections with SpaceX satellites in orbit and have played a crucial role in maintaining internet connectivity and communication within Ukraine, especially as the conflict disrupted the country's infrastructure.
SpaceX, in which Musk is the largest shareholder, began supplying thousands of Starlink satellite dishes to Ukraine shortly after Russia initiated its full-scale assault on its neighbouring country in February last year.
Responding to the claim, Musk said on X that SpaceX "did not deactivate anything" since the service had not been activated in those regions in the first place.
"There was an emergency request from government authorities to activate Starlink all the way to Sevastopol. The obvious intent being to sink most of the Russian fleet at anchor," Musk said.
"If I had agreed to their request, then SpaceX would be explicitly complicit in a major act of war and conflict escalation."