What happens now?

- The Kremlin said a signing ceremony on incorporating the new territories would take place on Friday in the Georgievsky Hall of the Great Kremlin Palace.

- Putin will give a speech, and meet with the leaders of the self-styled Russian-backed Donetsk People's Republic (DNR) and Luhansk People's Republic (LNR) as well as the Russian-installed leaders of the parts of the Kherson and Zaporizhzhia regions that Russian forces occupy.

- Russian-backed separatists and Russian-installed officials in the four partially Russian-controlled regions of Ukraine declared that voters had chosen to join Russia, in hastily organised "referendums" that the West said were illegal shams.

- "Kherson region, Zaporizhzhia, Donetsk People's Republic and Luhansk People's Republic will now forever be part of Russia," Kirill Stremousov, the Russian-installed deputy head of the Kherson region, said on Red Square.

- A stage with giant video screens has been set up on Moscow's Red Square, with billboards proclaiming "Donetsk, Luhansk, Zaporizhzhia, Kherson - Russia!"

- For Russia to formally annex the territories, some sort of treaty will be signed and then ratified by the Russian parliament, which is controlled by Putin allies. Moscow will then consider the areas part of Russia, and the "umbrella" of its nuclear defences will extend to them.

- Furthermore, their populations will be eligible to be drafted to fight for Russia against Ukraine, as men in the DNR and LNR, set up with Russian backing in 2014, already do.

- Ukrainian President Volodymyr Zelenskiy has repeatedly said that "pseudo-referendums" on annexation by Russia will destroy any chance of peace talks.

WHAT WILL THE WEST DO?

- The West and Ukraine say Russia is violating international law by seizing another part of Ukraine, whose post-Soviet borders Moscow recognised shortly after the fall of the Soviet Union. Putin's forces had already seized the Crimean Peninsula from Ukraine in 2014, and declared it part of Russia.

The West could increase arms supplies to Kyiv, and further tighten financial sanctions that are already the most severe imposed against a large economy in modern history.

- The areas that Russia is attempting to annex are not all under its control. From the Kremlin's perspective, once they are considered part of Russia, the front line of the conflict will run through Russian sovereign territory. That could prompt some sort of ultimatum from Russia to Ukraine and the West.

The Kremlin said on Wednesday that its "special military operation" in Ukraine must continue at least until the capture of all of eastern Ukraine's Donetsk region, of which it currently holds around 60%. The neighbouring Luhansk province, also part of the majority Russian-speaking industrial Donbas region, is almost entirely under Russian control.

(Reporting by Guy Faulconbridge; Editing by Peter Graff and Kevin Liffey)