Russians have strongly supported constitutional reforms that could keep President VLADIMIR PUTIN in power until 2036, partial results indicate.

The electoral commission said with about 87% of ballots counted, more than 77% of voters backed the measures.

The reforms would reset president PUTIN'S term limits to zero in 2024, allowing him to serve two more six-year terms.

Opposition members have said he is trying to become "president for life", a claim President PUTIN denies.

Several hundred opponents of the constitutional changes staged protests in Moscow and St Petersburg.

Voting began across Russia last week, and the electoral commission put turnout at more than 64%.