Russian President Vladimir Putin said on Wednesday he was introducing martial law in four Russian-occupied regions of Ukraine that Moscow claimed last month as its own territory but is struggling to defend from Ukrainian advances.

Russian President Vladimir Putin

In televised remarks to members of his Security Council, Putin boosted the security powers of all Russia's regional governors and ordered the creation of a special coordinating council under Prime Minister Mikhail Mishustin to step up the faltering war effort.

He said the "entire system of state administration", not only the specialised security agencies, must be geared to supporting what Russia calls its "special military operation".

The package of moves, nearly eight months into the war, marked the latest escalation by Putin to counter a series of major defeats at the hands of Ukrainian forces since the start of September.

The U.S. State Department said Russia was resorting to "desperate tactics". A Kyiv official said it would change nothing.

The published Kremlin decree ordered an "economic mobilisation" in eight regions adjoining Ukraine, including Crimea, which Russia invaded and annexed in 2014.

It placed them in a special regime one step below martial law and allowed for the restriction of people's movements.

Putin conferred additional powers on the leaders of all Russia's 80-plus regions to protect critical facilities, maintain public order and increase production in support of the war effort.

But it was far from clear how fast or how effectively the new measures might bolster Russia's military position on the ground. They came as Russian-installed officials in Ukraine's occupied Kherson region told civilians to leave some areas as soon as possible in anticipation of an imminent Ukrainian attack.

Russia expert Mark Galeotti said on Twitter the moves amounted to "a declaration of variegated martial law across the whole of Russia", with some level of emergency regulation now applying across the whole country.

He said it was unclear whether regional officials would use the extra powers as Moscow wanted, ignore them, or exploit them as opportunities to embezzle state resources.

The Russian-installed acting governor of occupied Kherson, Vladimir Saldo, confirmed that he would hand power to the military, according to Russian news agencies. But many regional chiefs - including Moscow's mayor Sergei Sobyanin - said they did not plan to make any immediate changes.

Ukrainian presidential adviser Mykhailo Podolyak said on Twitter: "This does not change anything for Ukraine: we continue the liberation and de-occupation of our territories."