Russian tycoon Oleg Tinkov on Tuesday denounced Moscow's "massacre" in pro-Western Ukraine and urged the West to help end "this insane war".

Offering some of the strongest criticism of the Kremlin's military action in Ukraine by a prominent Russian, Tinkov claimed online that 90 percent of Russians were "AGAINST this war" and called the country's forces a "shit army."

One of Russia's best-known entrepreneurs, Tinkov founded Tinkoff Bank in 2006. He has been based outside Russia in recent years.

Russian President Vladimir Putin sent troops to Ukraine on February 24 to "de-Nazify" the pro-Western country. The conflict has killed thousands of people and displaced more than 12 million in the largest refugee crisis in Europe since World War II.

"Waking up with a hangover, the generals realised that they have a shit army," Tinkov, 54, said in a post on Instagram.

"And how will the army be good, if everything else in the country is shit and mired in nepotism, sycophancy and servility?"

The businessman, who has been targeted by Western sanctions, added: "I don't see a SINGLE beneficiary of this insane war! Innocent people and soldiers are dying."

Tinkov attending an economic forum in Saint Petersburg in 2019
Tinkov attending an economic forum in Saint Petersburg in 2019 AFP / OLGA MALTSEVA

Switching to English, Tinkov, who stepped down as chairman of Tinkoff Bank in 2020, said:

"Dear 'collective West' please give Mr.Putin a clear exit to save his face and stop this massacre. Please be more rational and humanitarian."

He posted his statement on the 55th day of Moscow's military campaign, with Russian forces unleashing a major new offensive in the eastern Donbas region.

"90 percent of Russians ARE against this war!" Tinkov said. "Of course there are morons who draw Z but 10 percent of any country are morons," he said, referring to what has become a Russian symbol of support for the war.

He added that Kremlin officials were "in shock" that they and their children will no longer be able to spend their summer holidays on the Mediterranean. "Businessmen are trying to rescue what's left of their property," he added.

Russian authorities have sought to muffle dissent over Moscow's invasion of Ukraine, impose prison terms of up to 15 years for publishing "fake news" about the army.

Tinkoff Bank said in a statement it would not comment on Tinkov's "private opinion", saying he no longer took decisions regarding operations across companies under the Tinkoff brand.

"He is not a Tinkoff employee, has not been in Russia for a long time and has been dealing with health issues in recent years," the statement added.