Russian President Vladimir Putin formalised the annexation of four Ukrainian regions on Wednesday amid major battlefield reversals in recent days.

The reversal led to the shrinking amount of seized territory Moscow controlled.

Russia has escalated its seven-month war with the annexation drive, a military mobilisation and warnings of a possible recourse to nuclear weapons to protect all of its territories.

On Wednesday morning, the state-owned TASS news agency reported that Mr Putin signed off on a law formally incorporating the four regions, representing about 18 per cent of Ukraine’s territory, into Russia.

The Russian leader’s signature was the final stage in the legislative process; the two chambers of Russia’s parliament had already ratified the plan.

Kyiv and its Western allies said Russia’s attempted annexation was an illegal land grab and would never be recognised, with Ukraine saying its army would recapture any territory occupied by Russian forces.

Ukrainian President Volodymyr Zelensky said on Tuesday night that his military had made significant, rapid advances against Russian forces in the past week.

“This week alone, since the Russian pseudo-referendum, dozens of population centres have been liberated. These are in Kherson, Kharkiv, Luhansk and Donetsk regions altogether,’’ Mr Zelensky said.

The Ukrainian president named eight small towns in Kherson in the south recently recaptured. Reuters could not independently verify his statements.

Russia did not fully control any of the four regions it claimed Donetsk, Luhansk in eastern Ukraine, Zaporizhzhia, and Kherson in the south. The Kremlin said it had yet to determine the final borders of the annexed territory.

Andriy Yermak, head of Mr Zelensky’s office, reiterated the Ukrainian position on annexation.

Referring on Telegram to what he called a collective madhouse, he said worthless decisions by a terrorist country were not worth the paper they were signed on.

Russian forces in the Donetsk and Kherson regions were forced to retreat recently, and they dug in at new positions where they hoped to halt the Ukrainian advance.

Mr Zelensky said Ukraine had retaken territory in the rapid advance.

Moscow maps showed shrinking controlled areas as South Korea and the U.S. fired missiles into the sea to protest the “reckless” North Korea test.

(Reuters/NAN)