In a statement on Thursday, it said, "The city has been under blockade for 16 days, more than 350,000 Mariupol residents continue to hide in shelters and basements from continuous shelling by Russian occupation forces."

About 80 per cent of the city's housing stock has been hit, almost 30 per cent of which cannot be restored.

"BBC quoted Institute for the Study of War, a US think tank, as saying that Mariupol is likely to fall in coming weeks amid a sustained Russian assault.

The "total destruction" of Mariupol and increased targeting of its residential areas may lead to its capitulation or eventual capture, it pointed out.

Meanwhile, Mason Clark, lead Russia analyst at the institute, compared Russia's attack on Mariupol as being completely "ripped from the Syria playbook".

He said the tactics used by the Russian forces in Ukraine include "specific neighborhood-by-neighborhood targeting," less precise weapons that take a more brutal toll, and hitting civilian infrastructure.

He said, "They're very intentionally targeting water stations and power supplies and internet towers and cell phone towers and that sort of thing, in a very deliberate attempt to make it more difficult for the defenders to hold out and try and force them to capitulate. "It's the same approach the Russian forces have taken in a number of cities in Syria, such as Aleppo and Palmyra.

"You also then have the frankly deliberate war crimes that Russians are committing, such as targeting that drama theater in Mariupol that was housing refugees, which unfortunately tracks with what Russian forces have done in the past, both in Syria, as well as in previous wars in Georgia and Chechnya. "If Mariupol falls, that could be the "next major change in the war, because it'll free up a lot of Russian forces that are currently deadlocked in that operation, including some of the best units of Russia's Southern Military District that could potentially resume further operations," CNN quoted him as saying.