US President Barack Obama has imposed sanctions on 11 Russians and Ukrainians blamed for Russia's military incursion into Crimea, including two top aides to Russian President Vladimir Putin.

The European Union also will impose travel bans and asset freezes on 21 Russian and Ukrainian officials, it was announced Monday.

Obama's order freezes any assets in the US and bans travel into the country of 11 people named as responsible for the Russian move into Ukraine's Crimea region.

Among those sanctioned were ousted Ukraine President Viktor Yanukovich and Putin aides Vladislav Surkov and Sergei Glazyev.

The US sanctions came in an executive order signed by Obama a day after Sunday's Crimea referendum aimed at allowing Russia to annex the region, a vote that the US says was illegal and will never be recognised by Washington. The administration announced plans for sanctions earlier this month but had not named the individuals until Monday.

"Today's actions send a strong message to the Russian government that there are consequences for their actions that violate the sovereignty and territorial integrity of Ukraine, including their actions supporting the illegal referendum for Crimean separation," the White House said.

A senior Obama administration official said there was "concrete evidence" that some ballots in the Crimea referendum arrived in some Crimean cities pre-marked.

After a meeting lasting around three hours, the EU's 28 foreign ministers agreed on a list of those to be sanctioned for their part in Russia's seizure of Crimea and Sunday's referendum on joining Russia.

The ministers had "just agreed on sanctions - travel restrictions & assets freeze against 21 officials from Ukraine & Russia," Lithuanian foreign minister Linan Linkevicius wrote in a message on Twitter.

He said more measures would follow in a few days, when EU leaders meet for a summit in Brussels. They are expected to expand the list to include more senior figures closer to Russian President Vladimir Putin.

Following Sunday's referendum, Crimea's parliament "made a proposal to the Russian Federation to admit the Republic of Crimea as a new subject with the status of a republic," a statement on its website said.

The move, dismembering Ukraine against its will, would escalate the most serious East-West crisis since the Cold War.

The Kremlin and the White House issued statements saying Obama and Putin saw diplomatic options to resolve the dispute.

But Obama said Russian forces must first end "incursions" into its ex-Soviet neighbour while Putin renewed his accusation that the new leadership in Kiev, brought to power by an uprising that toppled his elected Ukrainian ally last month, were failing to protect Russian-speakers from violent Ukrainian nationalists.

Moscow responded to Western pressure for an international "contact group" to mediate in the crisis by proposing a "support group" of states. This would push for recognition of the Crimean referendum and urge a new constitution for rump Ukraine that would require it to uphold political and military neutrality. - Reuters