Speed restrictions on the key Starlink communications network have disrupted Ukraine's battlefield "missions", President Volodymyr Zelensky's adviser has warned.
Serhiy Beskrestnov said Ukrainian troops had not been informed about the speed limits set overnight at 100mph (160km/h) by Elon Musk's SpaceX company. A source in the Ukrainian defence ministry later confirmed this to the BBC.
Starlink is a vital tool allowing Kyiv to effectively guide drones to Russian targets and also protect Ukrainian skies. SpaceX has not publicly commented.
This comes as at least 600,000 people across Ukraine were left without electricity after deadly overnight Russian missile and drone strikes, Zelensky said.
He said "critical" energy infrastructure had been hit in Kyiv and the capital region, and in the north-eastern city of Kharkiv – despite US President Donald Trump's claim on Sunday that an "energy ceasefire" was in place between Russia and Ukraine.
Three people were killed in Kyiv, local officials said. Russia said its "massive" strikes had hit communications and energy facilities used by Ukraine's military.
Russian President Vladimir Putin launched a full-scale invasion of Ukraine in 2022, and Moscow currently controls about 20% of Ukrainian territory.
In Wednesday's post on Telegram, Beskrestnov said SpaceX had "implemented overnight a speed limit on Starlink terminals" and this had already resulted in "the disruption of a number of missions".
"It is clear that this action cannot be a coincidence and is related to the current political situation," he added.
In the follow-up post, Zelensky's adviser stressed that Starlink was the most effective tool for enabling interceptors to shoot down Russia's newly developed jet-propelled drones.
A source in the Ukrainian defence ministry later told the BBC: "Last night, we detected restrictions affecting Starlink connectivity at speeds above 160 km/h. The source added that the "root cause" of the issue was being investigated.
Defence ministry sources later explained that "once a vehicle or asset exceeds this [160km/h] threshold speed, the terminal loses its connection".
They told the BBC that this made it more difficult to carry out drone operations, "specifically interceptors and middle-strike drones", and also degraded "capabilities for front line logistics, reconnaissance, and signal relaying".
In February, Musk's decision to deny Russian forces access to Starlink blunted Moscow's advance in Ukraine and caused confusion among Russian commanders.
Musk's SpaceX has not commented on the reported speed restrictions.
Zelensky has said the US threatened to restrict intelligence sharing if he did not sign up to Trump's energy ceasefire. Trump on Tuesday denied that Washington was withholding intelligence.
Overnight, Russia had launched 39 ballistic and cruise missiles and 128 drones, and that four of those missiles and 115 drones had been shot down, according to Ukraine's air force.
It is the second night in a row Kyiv has been hit by Russian missiles, and came as Zelensky prepared to meet UK Prime Minister Andy Burnham at Downing Street on Wednesday to discuss accelerating air defence supplies to Kyiv.
During the past two nights, ballistic missiles have struck targets in the Ukrainian capital without any warning, before air raid sirens could be sounded.
Ukraine relies on US satellite systems to track Russian missiles in order to issue alerts and to try to shoot them down.
