Event marking Russia's annexation of four Ukrainian territories held in Luhansk
People gather near a screen showing Russian President Vladimir Putin during the broadcast of a ceremony to declare the annexation of the Russian-controlled territories of four Ukraine's Donetsk, Luhansk, Kherson and Zaporizhzhia regions, after holding what Russian authorities called referendums in the occupied areas of Ukraine that were condemned by Kyiv and governments worldwide, in Luhansk, Russian-controlled Ukraine, September 30, 2022. Reuters

The United States on Friday imposed sweeping sanctions on Russia over its declared annexation of a swath of Ukraine, targeting hundreds of people and companies, including those in Russia's military-industrial complex and members of the legislature.

The United States acted after Russian President Vladimir Putin on Friday proclaimed the biggest annexation in Europe since World War Two, declaring Russian rule over 15% of Ukraine.

"We will not stand by as Putin fraudulently attempts to annex parts of Ukraine," Treasury Secretary Janet Yellen said in a statement.

"The United States unequivocally rejects Russia's fraudulent attempt to change Ukraine's internationally recognized borders, including by holding sham 'referenda'," U.S. Secretary of State Antony Blinken said in a statement.

Russia's embassy in Washington did not immediately respond to a Reuters request for comment.

The U.S. Treasury Department said it imposed sanctions on 14 people in Russia's military-industrial complex, two leaders of the country's central bank, family members of top officials and 278 members of Russia's legislature "for enabling Russia's sham referenda and attempt to annex sovereign Ukrainian territory."

The Treasury also issued guidance warning of a heightened sanctions risk to those outside Russia should they provide political or economic support to Moscow.

Among those designated was Deputy Prime Minister Alexander Novak; 109 State Duma members; the Federation Council of the Federal Assembly of Russia and 169 of its members; and the governor of the Central Bank of Russia, Elvira Nabiullina.

Among the targets related to Russia's defense procurement was a Chinese supplier the Treasury accused of supporting Radioavtomatika, a U.S.-designated Russian defense procurement firm.

Washington said Sinno Electronics Co Ltd, previously placed on the Commerce Department's entity list, maintained a relationship with the Russian firm even after the invasion of Ukraine.

Sinno did not immediately respond to a Reuters request for comment.

Commerce also added 57 entities in Russia and Crimea to its U.S. export blacklist.

It also issued new guidance saying that U.S. restrictions on exports to Russia can apply to entities in other countries that support Russia's and Belarus's military and industrial sectors by shipping prohibited technologies and other items prohibited by the United States and the 37 countries with similar restrictions.

The U.S. State Department in a separate statement said it imposed visa restrictions on more than 900 people, including members of the Russian and Belarusian military and "Russia's proxies for violating Ukraine's sovereignty, territorial integrity, and political independence," barring them from traveling to the United States.

Russia declared the annexations after holding what it called referendums in occupied areas of Ukraine. Western governments and Kyiv said the votes breached international law and were coercive and non-representative.