YouTube and Facebook on Friday blocked several accounts with links to Ukrainian separatists as tensions soar between Moscow and the West over the possibility of Russia invading its ex-Soviet neighbour, separatists said.

The breakaway regions bordering Russia have been locked in an armed conflict with the Ukrainian army after Russia seized Crimea in 2014.

Several channels run by separatist authorities in self-proclaimed Lugansk People's Republic and Donetsk People's Republic were inaccessible.

The Lugansk People's Republic said on its official news website that its channels had been blocked "without explanation".

The channel of the Lugansk information centre was inaccessible on Friday and a service message said it "has been terminated for violating YouTube's community guidelines".

Several other separatist channels carried the same message, including those belonging to the ministry of information and the "people's militia" of the Donetsk stronghold.

Separately, Facebook blocked the page of the Lugansk "people's militia", a representative of the self-proclaimed republic told Russian state news agency RIA Novosti.

There was no immediate comment from the Silicon Valley giants.

Ukraine and its Western allies accuse Russia of supporting the separatists by sending arms and troops across the border. Moscow has denied the claims.

In recent months, Western leaders have sounded the alarm over a potential Russian invasion as Moscow has deployed more than 100,000 troops to the border with Ukraine.

Moscow insists it has no plans to invade Ukraine but has at the same time laid down a series of security demands -- including a ban on Ukraine joining NATO -- in exchange for de-escalation.