Russia's "massive" military losses in Ukraine are unsustainable, NATO's secretary general warned with the conflict about to enter its fourth year with no clear end in sight.

The prospect of another ally falling in the Middle East will be a worrying one for Moscow, particularly after it has seen other alliances collapse recently.

Russia said on Thursday that its was unacceptable for the West to keep claiming that Russia and China threatened Greenland, and said the crisis over the territory showed the double-standards of Western powers which claimed moral superiority.

Up to 25,000 Russian soldiers are being killed every month, NATO Secretary General Mark Rutte said this week.

It is difficult to determine how many foreigners have joined Russia's military. BBC Russian's analysis - which also looked at the number of foreigners killed and injured - suggests at least 20,000 may have signed up, including from countries such as Cuba, Nepal and North Korea.

Russia said on Thursday that using the language of blackmail and threats against Cuba was unacceptable after U.S. President Donald Trump told Havana to make a deal before it was too late.

Russia says it used its new Oreshnik hypersonic missile and other weapons in a massive strike on Ukraine​. Ukrainian President Zelenskyy says a drone hit the Qatar embassy.

Moscow said the overnight strike was in response to an alleged Ukrainian drone strike on a residence used by President Vladimir Putin, which the U.S. and others said did not happen.

Four years after David Barnes was charged in Russia with abusing his children in Texas despite not being charged with a crime in the U.S., he is now in a penal colony.

The Kremlin has tried for years to freeze Ukraine into submission. This winter, its attacks have been the most devastating ever.