Russian lawmakers on Monday voted unanimously in favour of legislation to annex four regions of Ukraine, rubber stamping a move that escalates the conflict and was already approved by Russian President Vladimir Putin.
Members of the Kremlin-loyal lower house of parliament, the State Duma, all voted to incorporate Donetsk, Lugansk, Kherson and Zaporizhzhia with no abstentions or votes against the annexation, its website showed.
Ukraine responded by officially lodging an application with the US-led military alliance NATO for membership and said it would never negotiate with Russia as long as Putin was in power.
Russia's Foreign Minister Sergei Lavrov, addressing parliament, appealed to lawmakers to back the bill to defend Russian language, culture and borders.
"We are not responding to imaginary threats, we are defending our borders, our Motherland and our people," he said.
He also claimed the United States had rallied all Western countries against Moscow to buttress Kyiv.
"The United States subjugated almost the entire collective West, mobilising it to turn Ukraine into an instrument for war with Russia".
Together, the five regions make up around 20 percent of Ukraine.
But Russian forces do not have complete control over Kherson or Zaporizhzhia and the Kremlin has not yet confirmed what areas of those regions are being annexed.