Moscow, Russia - The Kremlin on Monday rejected Ukraine's claims that Russian troops fighting on the frontline were using Starlink internet terminals.

Kyiv's GUR military intelligence agency said it had evidence that the terminals were being used on a "systematic" basis by Russian troops, accusing Moscow of "smuggling" them into the country.

Starlink, owned by Elon Musk's SpaceX, is a network of satellites in low Earth orbit that can provide internet to remote locations, or areas that have had normal communications infrastructure disabled.

"My companies have probably done more to undermine Russia than anything," Musk said during a streamed session on X, formerly known as Twitter, criticizing US funding to Ukraine.

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Musk maintained that SpaceX had taken away two thirds of Russian space launch business and that "Starlink has overwhelmingly helped Ukraine."

"It cannot be officially supplied here and is not officially supplied here," Kremlin spokesperson Dmitry Peskov told reporters on Monday.

"Accordingly, it cannot be officially used here in any way," he added.

The Starlink system is not active in Russia, meaning even a device inside Russia could not connect.

But Kyiv has accused Russian troops of using the device across the frontlines in Ukraine.

"Starlink is freely available in Russia. Compared to last year, now the use of Starlink in the Russian army on the front line has become more systematic," GUR spokesperson Andriy Yusov said Monday on state television.

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He said it would not "reveal all the details" of its claims.

Ukraine itself has widely used Starlink to ensure communications and connectivity for its troops during the two-year war.

Musk called reports SpaceX had sold Starlink terminals to Russia "categorically false" in a post on his X social media platform.

"To the best of our knowledge, no Starlinks have been sold directly or indirectly to Russia," he added.

Ukraine's Yusov said Kyiv accepted that Starlink was not "officially being sold to the Russians."

He said Russia bought them through "parallel imports, which is essentially smuggling."

Since Moscow invaded Ukraine and was hit with Western sanctions, it has set up a network of traders and intermediaries in third countries to get hold of banned goods and other products no longer available inside Russia.

It is not the first time Kyiv and Musk have clashed over Starlink.

Last year, the Tesla and SpaceX tycoon rejected a request to activate the network in the Crimean city of Sevastopol to support a Ukrainian attack on Russia's naval fleet.

He said SpaceX would have been "explicitly complicit in a major act of war and conflict escalation" if he had agreed.

Also last year, he said his company could not indefinitely fund the service in Ukraine, before agreeing to maintain the connections.