Scottish tennis star Andy Murray broke his silence over the independence referendum on Thursday by appearing to lend last-minute support to the "Yes" campaign as polling began.

"Huge day for Scotland today! No campaign negativity last few days totally swayed my view on it. Excited to see the outcome. Let's do this!" Murray wrote in a message to his 2.71 million followers on Twitter.

The last exclamation echoed the one used by pro-independence leader Alex Salmond in a fiery final campaign speech in Perth on Wednesday before polls for the historic vote opened on Thursday.

"Don't let them tell us we can't. Let's do this now," Salmond said.

Murray's message was re-tweeted over 14,000 times, including by Salmond himself, and became a top story on British media sites.

Glasgow-born Murray, 27, who is Britain's number one tennis player and won Wimbledon last year, does not live in Scotland and therefore cannot vote himself.

He divides his time between his house in Surrey, southeast England, and the United States.

But as one of Britain's most high-profile athletes, his apparent support for the "Yes" campaign is a boon for those who want Scotland to end its 307-year union with the United Kingdom.

Murray had previously been reluctant to back either side in the independence debate.

He sparked controversy in 2006 when he joked "anyone but England" when asked who he would support in that year's football World Cup and has quipped that he is considered British when he wins, but Scottish when he loses.

'Proud to be British'

He also criticised Salmond for unfurling a Scotland flag in the royal box at Wimbledon last year after he became the first Briton in 77 years to win the men's singles title.

Last month the two-time Grand Slam-winner told reporters in the United States: "If Scotland became independent, then I imagine I would be playing for Scotland."

But in an interview with The Times Magazine in March last year, he expressed reservations about independence.

"I don't think you should judge the thing on emotion, but on what is best economically for Scotland," he said.

"You don't want to come to a snap decision and then see the country go tits up. I am proud to be Scottish, but I am also proud to be British. I don't think there is any contradiction in that."

After taking time out following back surgery last year, Murray has slipped to number 12 in the global ranking.

He reached the semi-finals at this year's French Open, but failed to progress beyond the last eight at the other three Grand Slams. He lost to Novak Djokovic in the quarter-finals of the US Open earlier this month.

His brother, Jamie Murray, also a professional tennis player, was more explicit about his support for a "Yes" vote.

"Love UK... Love the Royals... but it's time for Scotland to stand on its own 2 feet and control their own destiny," he tweeted.

"Scotland is full of smart talented hard working humble people. Have faith in them to run our country successfully."