In the biggest expansion of Russian territory in at least half a century, the Russian president signs laws admitting Donetsk, Luhansk, Kherson and Zaporizhzhia regions into Russia.
President Vladimir Putin has completed the formal annexation of more than 15 percent of Ukraine, just as Russian forces battle to halt a Ukrainian counter-offensive across swathes of the territories.
In the biggest expansion of Russian territory in at least half a century, Putin signed on Wednesday laws admitting the Donetsk People's Republic (DPR), the Luhansk People's Republic (LNR), Kherson region and Zaporizhzhia region into Russia.
"Russian President Vladimir Putin has signed four federal constitutional laws on the entry of the Donetsk and Luhansk People's Republics, Zaporozhye and Kherson regions into the Russian Federation," the lower house of parliament said.
"He also signed the relevant laws on ratification."
Russia declared the annexations after holding what it called referendums in occupied areas of Ukraine. Western governments and Kiev said the votes breached international law and were coercive and non-representative.
The areas that are being annexed are not all under control of Russian forces. Russia's total claim amounts to around 18 percent of Ukrainian territory, though the exact borders are still to be clarified.
Putin's decision to annex the four regions has significantly raised the stakes in the seven-month conflict, with the European Union announcing an eighth round of sanctions against Moscow.
'Rapid and powerful' gains
Ukrainian President Volodymyr Zelenskyy said on Tuesday his forces were making "rapid and powerful" gains in southern Ukraine and that they had retaken "dozens" of villages from Russia this week.
Some of the territory was taken back in the regions of Kherson, Luhansk and Donetsk, he said, where the controversial referendums were held last week on being annexed by Russia.
Zelenskyy cited eight settlements in the southern Kherson region, where Moscow's forces have retreated in the face of a sweeping Ukrainian counter-offensive, according to maps presented by the Russian defence ministry on Tuesday.
Ukrainian forces have made a major breakthrough in the southern Kherson region this week, forcing Russian troops to abandon positions they had held since March.
But Kirill Stremousov, a Russian-backed official in Kherson region, said on Wednesday that the Ukrainian army's advance there had stopped, state-owned news agency TASS reported.
And in the eastern Donetsk region, Denis Pushilin, head of the Russian-backed separatist administration, said the frontline around the strategic town of Lyman, which Ukraine retook over the weekend, was "stabilising", according to another state-owned news agency, RIA.
British intelligence said on Wednesday Ukrainian armed forces had advanced up to 20 kilometres (12 miles) beyond the Oskil river in the northeastern Kharkiv region into Russia's defensive zone towards the town of Svatove in Luhansk region.
"Politically, Russian leaders will highly likely be concerned that leading Ukrainian units are now approaching the borders of Luhansk Oblast, which Russia claimed to have formally annexed last Friday," the British Ministry of Defence said in an intelligence bulletin.
The intelligence update added that it was highly likely that Ukraine could now strike the Svatove-Kremina road in Luhansk region and added that Ukraine continued to make progress is its operations in the southern front as well.