Russian President Vladimir Putin is poised to extend his nearly quarter of a century of rule for six more years after wrapping up an election that gave voters no real alternatives to an autocrat who has ruthlessly cracked down on dissent.

The three-day election that began on Friday has taken place in a tightly controlled environment where no public criticism of Mr Putin or his war in Ukraine is allowed.

His fiercest political foe, Alexei Navalny, died in an Arctic prison last month and other critics are either in jail or in exile.

The 71-year-old Russian leader faces three token rivals from Kremlin-friendly parties who have refrained from any criticism of his 24-year rule or his full-scale invasion of Ukraine two years ago.

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Russian President Vladimir Putin attends an electronic voting (Pavel Byrkin/Sputnik/Kremlin Pool Photo/AP)

Mr Putin has boasted of Russian battlefield successes in the run-up to the vote, but a massive Ukrainian drone attack across Russia early on Sunday sent a reminder of challenges faced by Moscow.

The Russian Defence Ministry reported downing 35 Ukrainian drones overnight, including four near the Russian capital. Moscow Mayor Sergei Sobyanin said there were no casualties or damage.

Russia’s scattered opposition has urged those unhappy with Mr Putin or the war to express their protest by coming to the polls at noon on Sunday. The strategy was endorsed by Mr Navalny not long before his death.

Voting is taking place at polling stations across the country’s 11 time zones, in illegally annexed regions of Ukraine and online.

More than 60% of eligible voters had cast their ballots as of early Sunday.

Despite tight controls, at least a half-a-dozen cases of vandalism at polling stations were reported on Friday and Saturday. A 50-year-old university professor was imprisoned on Saturday for 15 days after she tried to throw green liquid into a ballot box in the Urals city of Ekaterinburg, local news site Ura.ru reported.

In Podolsk, a town close to Moscow, a woman was fined 30,000 rubles (£254) and charged with “discrediting the Russian army” after spoiling her ballot with an unspecified message, according to OVD-Info, a police monitoring group.

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A woman holds her pet as she leaves a voting booth during a presidential election in the Pacific port city of Vladivostok (AP)

Ahead of the election, Mr Putin cast his war in Ukraine, now in its third year, as a life-or-death battle against the West seeking to break up Russia.

He has boasted about recent gains in Ukraine, where Russian troops have made slow advances relying on their edge in firepower.

Ukraine has fought back by intensifying cross-border shelling and raids, and by launching drone strikes deep inside Russia.

Air raid sirens sounded multiple times on Saturday in the Russian border city of Belgorod, where two people were killed by Ukrainian shelling, regional Governor Vyacheslav Gladkov said.

The defence ministry said it had thwarted attempts to enter the country by “Ukrainian sabotage and reconnaissance groups,” following claims by Ukraine-based Russian opponents of the Kremlin last week that they had made an armed incursion into the Belgorod and Kursk regions.

Western leaders have derided the election as a travesty of democracy.

Beyond the lack of options for voters, the possibilities for independent monitoring are very limited with no significant international observers were present.

Only registered, Kremlin-approved candidates, or state-backed advisory bodies, can assign observers to polling stations, decreasing the likelihood of independent watchdogs.