Several people have been detained for vandalism at polling stations on the first day of voting in presidential elections, Russian officials say.

Incidents involved green dye being poured into ballot boxes, the boxes being set alight and fireworks being set off inside polling stations, state media reported.

Vladimir Putin is certain to win six more years in office after the vote.

However, officials have called on law enforcement officers to be vigilant.

Voting is taking place in Russia over three days until Sunday. The result is not in doubt as Mr Putin has no credible opponent, however state-run media said that turnout had reached 23% by late afternoon in Moscow.

Most of the incidents were reported at polling stations in Moscow, Voronezh in south Russia, and the region of Karachay-Cherkessia in the north Caucasus, according to state news agency Tass.

BBC Verify has so far verified footage of six incidents across Russia, including a video showing a woman throwing a petrol bomb near a St Petersburg polling station.

Other authenticated videos showed paint being poured into ballot boxes at various polling stations. In one, a woman could be seen pouring bright green liquid into a box in Moscow. Another showed a fire breaking out at a voting booth.

Russia has also enforced the vote in occupied areas of Ukraine - in the small town of Skadovsk, Russian-appointed officials said an improvised device exploded in a rubbish bin in front of a polling station, but no one was hurt.

At least eight people have been arrested although officials have not said if the acts of vandalism were protests against Mr Putin.

According to some videos posted on Telegram, some of the people who vandalised the ballot boxes reportedly shouted pro-Ukrainian slogans.

The deputy chairman of Russia's Central Election Committee, Nikolay Bulayev, said on Friday there had been five incidents involving liquids being poured into ballot boxes.

According to Interfax news agency, the liquid was zelyonka ("brilliant green" in English) dye, which is an antiseptic solution but has been used in protests in Russia and Ukraine.

Election Commission chief Ella Pamfilova described the saboteurs as "scumbags" and said some of those detained for vandalising the boxes with dye admitted that they had done it for money. They could be jailed for up to five years, she added.

One of those detained had been promised 100,000 roubles (£850; $1,080), she was quoted as saying.

Yulia Navalnaya, the widow of Mr Putin's most vocal critic, has called on Kremlin opponents to go en masse to polling stations at noon on Sunday to protest against the election. Her husband, Alexei Navalny, died suddenly in an Arctic Prison last month.

Ms Navalnaya has urged the West not to recognise Mr Putin's fifth term as president and Nato's secretary general has said the vote will not be free and fair.

Polling stations opened in the Kamchatka Peninsula, Russia's easternmost region, at 08:00 local time on Friday (20:00 GMT on Thursday) and will finally close in the westernmost Kaliningrad exclave at 20:00 on Sunday.