Russia's President Vladimir Putin has signed laws absorbing four Ukrainian regions into Russia, a move that finalises the annexation carried out in defiance of international law.
Earlier this week, both houses of the Russian parliament ratified treaties making the Donetsk, Luhansk, Kherson and Zaporizhzhia regions part of Russia.
The formalities followed Kremlin-orchestrated referendums in the four regions, which Ukraine and the West have rejected as a sham.
It's the biggest expansion of Russian territory in at least half a century, and Russia's total claim amounts to around 18 per cent of Ukrainian territory, though the exact borders are still to be clarified.
"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 does not fully control any of the four regions, with only around 60 per cent of the Donetsk region in Russian hands.
Even as the laws were being signed, Ukraine claimed further victories, recapturing towns within the annexation zone.
The ballots that proceeded Wednesday's formalities have been widely discredited and residents who escaped to Ukrainian-held areas have said people had been forced to vote in the street by roving officials at gunpoint.
'Four new regions of Russia'
Announcing the annexations at a major speech held at the Kremlin on Friday, Mr Putin declared the move was "the will of millions of people".
"People have made their choice at referendums in Ukraine's territories," he said.
"There are four new regions of Russia."
The annexed regions' pro-Moscow administrators were at the ceremony in the ornate St Georges Hall to sign treaties to join Russia in front of hundred of dignitaries.
At the ceremony, Mr Putin said the people living in the annexed regions were now Russian compatriots "forever".
The borders of the territories Russia has claimed remain unclear, but the Kremlin has vowed to defend Russia's territory — the newly absorbed regions, too — with any means at its disposal, including nuclear weapons.
Ukrainian President Volodymyr Zelenskyy responded to the annexation by announcing a fast-track application to join NATO and formally ruling out talks with Russia.
Mr Zelenskyy's decree, released on Tuesday, declares that holding negotiations with Mr Putin has become impossible after his decision to take over the four regions of Ukraine.
On Saturday, Ukraine's Ambassador to Australia insisted the Kremlin signing ceremony "doesn't change anything" for the country.
Vasyl Myroshnychenko said Russia's annexation was "propaganda" and "fake".
"Their so-called referendums were done at gunpoint, and we've seen how it was organised, so there is no validity in any of that," he told the ABC.
Russia — which recognised Ukraine's post-Soviet borders in the 1994 Budapest Memorandum — will never give the regions back, Mr Putin said on Friday.
According to Russia's parliament, people living in the annexed regions will be granted Russian passports, the Russian Central Bank would oversee financial stability and the Russian rouble would be the official currency.
On September 21, Mr Putin ordered Russia's first mobilisation since World War Two, calling up 300,000 reservists, in the biggest escalation of the Ukraine war since Moscow's February 24 invasion.
Russia's Defence Minister Sergei Shoigu was cited by the RIA news agency on Tuesday as saying that Russia had so far called up more than 200,000 men.
Many Russian men have fled the country rather than fight in Ukraine.
Ukrainian forces retake more territory
Ukrainian forces took back three more settlements in the southern Kherson region on Wednesday, Mr Zelenskyy said in a late-night video address.
Mr Zelenskyy named the three as Novovoskresenske, Novohryhorivka and Petropavlivka, which all lie to the north-east of the city of Kherson.
Russian troops also started to withdraw from a southern Ukrainian city that was annexed along with the Kherson region, though it administratively belongs to the neighbouring Mykolaiv area, said Mykolaiv governor Vitaliy Kim on Wednesday.
Mr Kim said officials are "seeking to confirm that officers have left Snihurivka, but there are troops still remaining there".
Earlier, a Russia-installed official, Yury Barbashov, admitted Ukrainian troops were advancing toward the city but claimed Russia was still in control.
Snihurivka, a city of 12,000, is a strategic railway hub in the Mykolaiv region. The Russians have seized the city in March and then annexed it together with the neighbouring Kherson region.
In the eastern Luhansk region, the governor Serhiy Haidai said on Wednesday that Ukrainian forces had retaken several localities in the region, which were also among the four illegally annexed by Moscow.
"The de-occupation of the Luhansk region has begun, we can talk about it officially — several settlements have been liberated from the Russian army and the invaders," Mr Haidai said in a video statement on Telegram.
He said the retreating Russian forces "are trying to mine everything as much as possible — roads, buildings, everything around".
Mr Haidai did not name the recaptured places, but earlier on Wednesday, Kyiv's Operational Command South said that the Ukrainian flag has been raised above Liubymivka, Khreschenivka, Zolota Balka, Biliaivka, Ukrainka, Velyka and Mala Oleksandrivka villages.
'Kamikaze' drone attacks
On Wednesday morning, on the battlefield, multiple explosions rocked Bila Tserkva, setting off fires at what were described as infrastructure facilities in the city to the south of the capital Kyiv, regional leader Oleksiy Kuleba said.
Early indications are that the city was attacked by so-called "kamikaze" or suicide drones, he said.
Bila Tserkva is about 80 kilometres south of Kyiv.
Russia has increasingly been using suicide drones in recent weeks, posing a new challenge to Ukrainian defences.
The unmanned vehicles can stay aloft for long periods of time before diving into their targets and detonating their payload at the last moment.
Many of the earlier attacks by the Iranian-made drones happened in the south of the country and not near the capital, which hasn't been targeted for weeks.
Mr Kuleba said that a total of six Shahed-136 drones struck the city, one of the largest in the region after Kyiv itself.
One person was injured in the attacks.
Dozens of rescue workers were on the scene and still working to extinguish the fires hours after the attacks were reported, he said.
US President Joe Biden told Mr Zelenskyy on Tuesday the United States would provide Ukraine with $US625 million ($964 million) in new security assistance, including High Mobility Artillery Rocket System (HIMARS) launchers.
Wires/ABC
