Russian state investigators in Moscow said on Friday they had opened a criminal case against a woman who poured green dye into a ballot box to try to disrupt voting in the country's presidential election.

Russians began to cast their ballots across the country's 11 time zones on Friday, the start of a three-day election that is almost certain to hand Vladimir Putin six more years at the helm of the world's biggest nuclear power.

CCTV footage released of the incident by the RIA state news agency showed a young woman depositing her voting slip before calmly pouring a green liquid into the transparent plastic ballot box.

A policeman is seen detaining her immediately afterwards.

The woman, who was not named, was later charged with "obstructing the exercise of electoral rights or the work of election committees," the Investigative Committee's press service said.

Such an offence carries a maximum punishment of five years in jail.

Two similar incidents occurred at polling stations in the Voronezh region, RIA reported.

(Reporting by Reuters; Editing by Andrew Osborn)