People linked to unrest in Crimea face freeze on assets and travel ban after referendum vote in favour of union with Russia

The US and the European Union have retaliated over the Crimea referendum by targeting sanctions against Russians and Ukrainians.

European foreign ministers imposed EU-wide sanctions on Monday against 21 Russian and Ukrainian officials linked to unrest in Crimea. Washington followed up an hour later with a list of its own, targeting seven top Russian government officials and politicians and four Crimea-based separatist leaders accused of undermining the "democratic processes and institutions in Ukraine".

Barack Obama is to visit Europe next week for discussion of the crisis with allies. Speaking to journalists at the White House, he said the new sanctions increase the costs on the Russian government for its actions

"If Russia continues to interfere in Ukraine, we stand ready to impose further sanctions," Obama said.

A man reads a newspaper with the headline 'Crimea chooses Russia' on a street in Simferopol. Photograph: Sergei Karpukhin/Reuters

He added: "We will continue to make clear to Russia that further provocations will achieve nothing except to further isolate Russia and diminish its place in the world." The White House said the sanctions were "by far and away the most comprehensive sanctions since the end of the cold war", and rejected criticism that they were too limited in scope or would be easily circumvented by asset transfers.

"We think they will be effective," one senior administration official told reporters in Washington. "No US business can do business with them – that will have impact on some or all of these individuals. If they want to transact in dollars, for example, they will be unable to do so and will tend to have difficulty in accessing financial services in Europe, the Middle East or Asia."

Another US official said the list included the "key architects and ideologues responsible for [the Crimea] policy" but they were also responsible for human rights abuses in Russia.

The White House reiterated its current opposition to extending the list to include Vladimir Putin, saying it would be an extraordinary step to target a head of state in that way, but left open the possibility of expanding sanctions in reaction to further escalation by Russia.

The US president said that if Russia did not back off, it could expect additional sanctions. Russia responded by insisting the sanctions would have little impact.

The punitive measures came on the eve of an address to the Russian parliament by President Vladimir Putin on Crimea. He is expected to take steps to formalise the incorporation of Crimea into Russia but, if he felt the need to try to slow the imposition of sanctions, he could opt for a more measured response.

The sanctions follow the referendum in Crimea on Sunday, in which there was an overwhelming vote in favour of union with Russia. The EU condemned the referendum as illegal and said it would not recognise the outcome.

Washington alleged multiple election violations during and leading up to the referendum.

"There has been broad speculation and some concrete evidence that ballots that arrived in Crimea for the referendum had been pre-marked in many cities," said a senior US administration official. "There are massive anomalies in the vote, even as it is recorded, including the fact that, based on census in Sevastopol city, 123% of the Sevastopol population would have had to have voted yes for the referendum."

European ministers and EU officials said the 21 people – mainly political figures involved in the breakaway of Crimea rather than business figures – would face a freeze on assets as well as a travel ban. That number could be expanded later in the week, they added.

It is notoriously difficult to secure EU agreement on sanctions anywhere because they require unanimity from the 28 member states. There were wide differences over the numbers of Russians and Crimeans to be punished, with countries such as Greece, Cyprus, Bulgaria and Spain reluctant to penalise Moscow for fear of closing down channels of dialogue. The 21 named were on an original list that ran to about 120 people.

The Dutch foreign minister, Frans Timmermans, described sanctions as inevitable, saying: "I hope the Russians will realise that sanctions will hurt everyone, but no one more than the Russians themselves."

Expanding the numbers on the sanctions list is almost certain to be discussed at the EU summit on Thursday and Friday. Some EU states are torn about taking punitive measures against Russia for fear of undoing years of patient attempts to establish closer ties with Moscow as well as increase trade. The EU has already suspended talks with Russia on an economic pact and a visa agreement.

The aim of some members is to gradually increase sanctions, just as the EU did with Iran, to put pressure on Putin.

The German foreign minister, Frank-Walter Steinmeier, said any measure must leave "ways and possibilities open to prevent a further escalation that could lead to the division of Europe".

After the breakdown of 11th-hour talks in London on Friday with his Russian counterpart Sergei Lavrov, the US secretary of state, John Kerry, hinted that a new diplomatic window might open after the referendum. But there is no sign yet of any compromise by Russia.

The seven Russians targeted by US sanctions



Vladislav Surkov, a Putin aide

Sergey Glazyev, a Putin adviser

Leonid Slutsky, a state Duma deputy

Andrei Klishas, member of the Federation Council (the upper house of the Federal Assembly of Russia)

Valentina Matviyenko, head of the Federation Council

Dmitry Rogozin, deputy prime minister

Yelena Mizulina, a state Duma deputy