Reuters published this article:

Russian President Vladimir Putin said the situation in four areas of Ukraine that Moscow has unilaterally declared part of Russia was proving "extremely difficult", one of his clearest public admissions yet that his invasion is not going to plan.

He also called for an increase in surveillance in his comments to mark Security Services Day in Russia on Tuesday. They followed a visit to close ally Belarus that fuelled fears, dismissed by the Kremlin, that the country could help Russia open a new invasion front against Ukraine.

Kyiv renewed calls for more weapons after Russian drones hit energy targets in a third air strike on power facilities in six days.

Putin ordered the Federal Security Services (FSB) to step up surveillance of Russian society and the country's borders to combat the "emergence of new threats" from abroad and traitors at home. Western countries have imposed unprecedented sanctions on Russia and the rouble slumped to an over seven-month low against the dollar on Tuesday after the European Union agreed to cap prices of gas, a major Russian export.

In a rare admission of the invasion of Ukraine not going smoothly, Putin cautioned about the difficult situation in regions of Ukraine that Moscow moved to annex in September and ordered the FSB to ensure the "safety" of people living there.

"The situation in the Donetsk and Luhansk People's Republics, in the Kherson and Zaporizhzhia regions is extremely difficult," Putin said in a video address to security workers translated by Reuters.

In September, Putin sought to regain the initiative after a series of battlefield defeats by declaring that four partially occupied regions in Ukraine's east and south had joined Russia. Kyiv and its Western allies said the move was illegal.

In October, Russian forces drew back in one of the regions - Kherson - and dug in elsewhere. They have failed to gain ground and earlier this month, Putin said the war could be a "long process".

On Monday, Putin made his first visit to Belarus since 2019, where he and his counterpart extolled ever-closer ties at a news conference late in the evening but hardly mentioned Ukraine. On Tuesday, Russian news agencies reported that Belarus had reached an understanding with Moscow on the restructuring of its debt and had agreed on a fixed price for Russian gas for three years.

Kyiv, meanwhile, was seeking more weapons from the West after weeks of attacks on energy facilities which have knocked out both power and water supplies amid freezing temperatures.

"Weapons, shells, new defence capabilities ... everything that will give us the ability to speed up the end to this war," President Volodymyr Zelenskiy said in his evening address.

Ukraine's military said it had shot down 30 of 35 "kamikaze" drones fired by Russia on Monday, mostly at the capital Kyiv. The unmanned aircraft fly towards their target, then plummet and detonate on impact.

Ukrainian officials said on Tuesday that five people had been killed in the eastern Donetsk and southern Kherson regions, with eight wounded, and that 21 missiles had knocked out power in the southern city of Zaporizhzhia.