WASHINGTON/MOSCOW. US President Barack Obama announced new sanctions against prominent Russians, including close allies of President Vladimir Putin, as Moscow raced to complete its annexation of Crimea.

Moscow on Thursday responded by announcing its own sanctions against senior US politicians in retaliation against visa bans and asset freezes imposed by Washington on its citizens.

The Russian foreign ministry said US action against Moscow would "hit the United States like a boomerang” and warned it would respond to "every hostile thrust”.

With Obama also clearing the way for possible sanctions on vital sectors of the Russian economy, Putin told Russian company bosses to bring their assets home to help the nation survive the sanctions and an economic downturn.

Obama said the action would also target a Russian bank, named by a senior administration official as Bank Rossiya, which is partly owned by Yuri Kovalchuk, a St. Petersburg banker whose association with Putin dates back to the early 1990s.

Speaking at the White House, Obama said Russia’s threats to southern and eastern areas of Ukraine - which like Crimea have large Russian-speaking populations - posed a serious risk of escalating the crisis in the region.

"We’re imposing sanctions on more senior officials of the Russian government,” he said.

"In addition, we are today sanctioning a number of other individuals with substantial resources and influence who provide material support to the Russian leadership, as well as a bank that provides material support to these individuals.”

Duma approves annexation

The president’s remarks came after the Russian parliament’s lower house gave its near-unanimous approval to the country’s annexation of Crimea, ignoring threats of more sanctions.

The Kremlin-controlled Duma voted 445-1 on Thursday to make Crimea a part of Russia following a quick discussion in which members assailed the Ukrainian authorities.

The vote came as UN Secretary-General Ban Ki-moon arrived in Moscow for a meeting with Putin. "I’m deeply concerned about the current situation,” Ban said at the start of the talks.

The incorporation of Crimea into Russia needs to be rubber-stamped by the upper house and receive a final endorsement by Putin, formalities expected to be completed by the end of the week.

During Thursday’s debate, senior politicians spoke of the need to protect Russian speakers elsewhere in Ukraine from radical Ukrainian nationalists, statements that could fuel fears of Russian invasion.

"They don’t understand in Washington that entire territories will flee as Crimea did if such outrage continues,” said Vladimir Vasilyev, the leader of the dominant United Russia faction.

Though Putin, who signed the treaty for Crimea to join Russia earlier this week, said he is not seeking a division of Ukraine, he insists the country can "use all means” to protect Russian speakers.

He also made his view clear that he sees Ukraine as an artificial state carved up by the Soviet government to include some of Russia’s historic lands.