New restrictions on the speed at which some of Ukraine's weapons can travel and stay connected to the Starlink internet network have disrupted Ukraine's battlefield "missions", President Volodymyr Zelensky's adviser has warned.

Serhiy Beskrestnov said Ukraine had not been told about speed limits set overnight at 100mph (160km/h) by Elon Musk's SpaceX company.

Starlink is a vital tool allowing Kyiv to effectively guide drones to Russian targets and also protect Ukrainian skies.

Beskrestnov said SpaceX's move "cannot be a coincidence and is related to the current political situation". The firm has not commented.

In Wednesday's post on Telegram, Beskrestnov said that SpaceX had "implemented overnight a speed limit on Starlink terminals" and this had already resulted in "the disruption of a number of missions".

In a follow-up post, the adviser stressed that Starlink was the most effective tool for enabling interceptors to shoot down Russia's newly developed jet-propelled drones.

It comes as at least 600,000 people across Ukraine were left without electricity after deadly overnight Russian missile and drone strikes, Zelensky said. Pictures from Kyiv showed residents, some dressed in their pajamas, with bloodied faces.

He added that "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 reported. Russia said its "massive" strikes had hit communications and energy facilities used by Ukraine's military.

Later on Wednesday, at least six people were killed in a Russian drone strike on a warehouse in the north-western city of Lutsk, local officials said.

Russian President Vladimir Putin launched a full-scale invasion of Ukraine in 2022, and Moscow currently controls about 20% of Ukrainian territory.

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 that the US threatened to restrict intelligence sharing if he did not sign up to Trump's energy ceasefire. On Tuesday, Trump denied that Washington was withholding intelligence.

Ukraine relies on US satellite systems to track Russian missiles in order to issue alerts and to try to shoot them down. But over the past two nights, missiles have struck targets in the Ukrainian capital without any warning, before air raid sirens could be sounded.

According to Ukraine's air force, Russia launched 39 ballistic and cruise missiles and 128 drones overnight. Four of those missiles and 115 drones were shot down, it said.

It was the second night in a row that Kyiv was 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.

Meanwhile, the Russian defence ministry said 902 Ukrainian drones had been shot down overnight over a number of Russian regions, including the capital Moscow and Crimea - Ukraine's southern peninsula annexed by Russia in 2014.

On Sunday, Trump wrote on Truth Social: "Effective immediately, there is an ENERGY CEASEFIRE in the War between Russia and Ukraine. Both parties have agreed. Do not break it!"

Zelensky has since repeatedly said that Ukraine is ready to halt its strikes on Russian oil refineries and other energy facilities if Moscow does the same.

But Russia's Foreign Minister Sergey Lavrov has said Ukraine does not deserve the "respite" a ceasefire would bring. Under any truce, he added, Europe would be able to "pump [Ukraine] with new weapons", enabling it to continue the war.

For residents of Kyiv, the past two nights have been frightening.

Tetiana Storozhyk, 54, said a late night blast on Tuesday at her apartment block blew her from the kitchen into the hallway. The sirens sounded just as the missile hit the building, giving her no time to evacuate.

"It all happened in a fraction of a second. In that moment I lost everything" she said.

Storozhyk told the BBC that Ukraine needs weapons to protect its people, "but from the other side we need peace".

Without peace Ukraine is reliant on its air defences, but this wrecked neighbourhood is evidence of how ineffective they are without the right data.