Mr Obama also yesterday said he had signed an order enabling the US to impose sanctions on sectors of the Russian economy.
It came as EU leaders have arrived in Brussels amid warnings they may also impose tougher economic sanctions.
Tensions remain high as Moscow approves a treaty enabling Crimea, an autonomous republic in Ukraine, to join Russia.
Among the people sanctioned are Sergei Ivanov, chief of Russia’s presidential staff, and Arkady Rotenberg and Boris Rotenberg, Putin’s childhood friends and former judo sparring partners.
The brothers are reported to be worth $2.2 billion (£1.3bn) and $1.4bn respectively. They have held big state contracts, and Arkady Rotenberg’s companies won billions in road contracts in Sochi, the host of the 2014 Winter Games.
Others include Gennady Timchenko, a founder of Gunvor, one of the world’s largest independent commodity trading companies involved in oil and energy, and Vladimir Yakunin, chair of the state-owned company Russian Railways since 2005, who was targeted because of his official position in the Russian government. He is a close confidant of Putin’s, and accompanies him on many domestic and international trips.
Sanctions were also imposed on Bank Rossiya, the personal bank for senior officials of the Russian Federation.
Rossiya is reported be the 17th largest bank in Russia and maintains numerous ties to banks in the US, Europe and elsewhere, with customers including many in the oil, gas and energy sectors.
Announcing the further sanctions, Mr Obama said: “Russia must know that further escalation will only isolate it further from the international community.”
And EU leaders last night said they will hit more people with a travel ban and asset freeze, closing in on Mr Putin’s inner circle.
They also announced plans to scrap a scheduled EU-Russia summit in June as part of the intensifying standoff over Ukraine, which has turned into one of the biggest political crises in Europe since the Cold War.
“We need to prepare to take further steps and we need to do it together,” said Swedish prime minister Fredrik Reinfeldt.
Germany’s chancellor Angela Merkel said beyond increasing the number of Russians and Crimeans affected by asset freezes and travel bans – initially at 21 politicians and military commanders – the leaders would prepare stronger measures for future use, which would include economic sanctions and an arms embargo.
Prime Minster David Cameron said the two-day summit would also focus on strengthening Ukraine’s fledgling government, calling on the 28 EU nations’ need to bolster the new Ukrainian authorities with political commitments and economic aid.
President Dalia Grybauskaite of Lithuania said the EU would not be far behind the United States in imposing further sanctions.
He said: “It is already time to target the close circle of Putin. This list is not yet large enough and sufficient and is very low-level.”
Beyond punishing Russia, the EU also wanted to show backing for Ukraine, which lost Crimea to Moscow on Tuesday.
Ukraine’s prime minister Arseniy Yatsenyuk will sign a political agreement today with EU leaders, underscoring Europe’s commitment to the new leadership in Kiev.
Speaking to France-24 television from Brussels, he called the agreement “the first big tremendous step to make Ukraine really a part of big Europe. We do understand that this is only the first step.
“But this will pave the way to real reforms that my country urgently needs.”
Despite the tough talk, there also is concern in Europe about inflicting too much economic damage as the continent crawls out of a crippling financial crisis.
The EU is Moscow’s biggest trading partner, and Russia is the EU’s third-largest partner, mostly thanks to exports of raw materials such as oil and gas. Because of the multi-billion trade exchanges, any step toward economic sanctions will not be taken lightly.
“The Russian economy is already hurt by what Putin is doing,” Mr Reinfeldt said, adding that a spree of retaliatory sanctions would hurt everyone.