LONDON, Oct 5 (AFP) - President Vladimir Putin completed the formal annexation of more than 15% of Ukraine on Wednesday just as Russian forces battled 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 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 Lugansk 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 Kyiv 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% of Ukrainian territory, though the exact borders are still to be clarified.

Russian defence ministry maps presented on Tuesday appeared to show rapid withdrawals of Russian invasion forces from areas in eastern and southern Ukraine where they have been under severe pressure from a Ukrainian counteroffensive.