Russian businessman Yuri Kovalchuk
Russian businessman Yuri Kovalchuk - Putin's bankerReuters

Sanctions against 20 Russian officials and "cronies who held significant resources" have targeted President Vladimir Putin's inner circle and a bank as the US turns up the heat in protest at Russia's invasion and annexation of Crimea.

Among those targeted are billionaire allies, friends, Kremlin ideologues and close confidants of Putin since 1993. The list includes Putin's chief of staff Sergey Ivanov, banker Yuri Kovalchuk and lifetime friends.

On the list are:

Rossiya Bank The 17th largest bank in Russia with $10bn in asset, according to a senior administration official, who said the bank would be "frozen out of the dollar" and the US would work to "prevent it from operating to the greatest extent possible".

Arkady and Boris Rotenberg The most influential businessmen in Russia. They were judo sparring partners with Putin and remain close. From 2008, the Rotenbergs started acquiring subsidiaries of Russian energy giant Gazprom and built them into Stroygazmontazh Corporation (or SGM Group), one of the biggest construction contractors in the energy field. Arkady is the president of the multi-championship-winning hockey club Dynamo Moscow. His net worth is $4bn, according to Forbes.

The US Treasury said: "They have made billions of dollars in contracts for Gazprom and the Sochi Winter Olympics awarded to them by Putin. Both brothers have amassed enormous amounts of wealth during the years of Putin's rule in Russia. The Rotenberg brothers received approximately $7 billion in contracts for the Sochi Olympic Games and their personal wealth has increased by $2.5 billion in the last two years alone."

Russian businessman Gennady Timchenko
Russian businessman Gennady TimchenkoReuters

Gennady Timchenko One of the most powerful people in Russia and co-owner of the international energy traders Gunvor Group. He once sued The Economist for calling him Putin's friend. He is chairman of the board of KHL, the Russian national hockey league, and president of the SKA St Petersburg Hockey Club. In December, he was awarded the Order of Friendship from Putin, an important government honour.

The US Treasury said: "Putin has investments in Gunvor and may have access to Gunvor funds".

Yuri Kovalchuk Also a close friend of Putin from the time he was deputy mayor of St Petersburg. He is the largest shareholder of Rossiya Bank and owns stakes in six federal TV channels. His net worth is $1.4bn, according to Forbes. He is often called "Putin's banker" and has been referred to as one of his "cashiers".

Vladimir Yakunin
Vladimir YakuninReuters

Vladimir Yakunin One of the most powerful men in Russia, president of the state-run Russian Railways company.

The US Treasury said: "Yakunin is being designated because of his official position in the Russian government, but he is also a close confidant of Putin".

Sergei Mironov Russian politician leader and head of pro-Kremlin Fair Russia parliamentary faction.

The US Treasury said that as a result of these sanctions "any assets of the persons designated today that are within US jurisdiction must be frozen".

"Additionally, transactions by US persons or within the United States involving the individuals and entity designated today are generally prohibited," reads a statement.