"The situation in the Donetsk and Lugansk People's Republics, in the Kherson and Zaporizhzhia regions is extremely difficult," Putin told the Russian security services on their professional holiday.

Putin singled out those working in the "new regions of Russia".

"The people living there, the citizens of Russia, rely on you, on your protection," he said.

Putin also said that "maximum composure, concentration of forces" was required of Russia's counterintelligence operations.

"It is necessary to strictly suppress the actions of foreign intelligence services, to quickly identify traitors, spies and saboteurs," he added.

Putin in September announced the Russian annexation of four territories in the east and south of Ukraine after Moscow proxies held referendums there, denounced as a sham by Kyiv and the West.

But Russian troops at no point controlled all of any of these regions, and last month were forced out from the regional capital of the southern Kherson region after a months-long Ukraine counteroffensive.

Following setbacks on the ground, Moscow switched strategies and stepped up its aerial campaign, targeting Ukraine's military and energy facilities.