Nearly 78% of Russian voters backed constitutional reforms that could keep President Vladimir Putin in power until 2036, election officials say.
With all the ballots counted, 77.9% voted for the reform package and 21.3% against, the electoral commission said.
The reforms will reset Mr Putin’s term limits to zero in 2024, allowing him to serve two more six-year terms.
Opposition figures denounced the vote, saying he was aiming to be “president for life”, a claim Mr Putin denies.
The Kremlin hailed the vote as a “triumph” and Mr Putin thanked Russians for their “support and trust”, adding that they were “improving the political system, firming up social guarantees, strengthening sovereignty and territorial integrity”.
However, there was no independent scrutiny of the seven-day vote, and copies of the new constitution appeared in bookshops during the week.
By spreading out the vote, because of the coronavirus infection risk, the authorities made any monitoring of it more difficult.
Top Kremlin critic Alexei Navalny described the results as a “big lie” which did not reflect real public opinion in the country.
Mr Putin is already the longest-serving leader in modern Russian history since Soviet dictator Joseph Stalin. A US state department spokeswoman said it was troubled by “reports of voter coercion, pressure on opponents of the amendments and restrictions of independent observers of the vote”, AFP reported.
Golos, an independent Russian election monitoring group, has castigated the vote, alleging there were many violations of democracy.
Its criticisms include: opponents were barred from campaigning in the media; remote electronic voting was organised on an illegal basis; election monitors were appointed by the Civic Chamber – a government body.
Golos describes it as “just a PR exercise from the very start” and says “there was no legal need for it”. The vote “will go down in history as an attack on the sovereignty of the people”.