Political optimism has been tempered by allegations of polling station intimidation as voting in the General Election entered full swing in Scotland.

SNP heavyweight Alex Salmond insisted his party's "tails are up across the country" as he cast his vote in Ellon, in the Gordon constituency where he is standing.

Mr Salmond joined SNP voter Nicki Falconer, who voted for the first time in last year's independence referendum and has since joined the party.

SNP leader Nicola Sturgeon said Scotland's political future is now "in the hands of the voters" after voting early at Broomhouse community hall in Glasgow accompanied by husband and SNP chief executive Peter Murrell.

But Scottish Conservative leader Ruth Davidson took to Twitter with allegations of voter intimidation in Dumfriesshire, Clydesdale and Tweeddale, where Scotland's only Tory MP David Mundell is hoping for a return to Westminster.

She said: "Disturbing reports of people being turned away from an Annan polling station by burly blokes if they say they don't support a certain party."

Police Scotland and Dumfries & Galloway Council said they are currently looking into the allegations.

Scottish Labour leader Jim Murphy said "the sun is shining and there is a huge amount of energy and confidence" in the party as he voted at Busby Primary School in the East Renfrewshire constituency he has represented since 1997.

"I've always been the underdog in this constituency," he said.

"It's usually the Tories who are favourites but the bookies say this time round it's the SNP, but I always enjoy confounding the pollsters, the pundits and the bookies. We've had a great response."

Former Labour shadow foreign secretary Douglas Alexander said "a Labour government is within touching distance" as the polls opened in Paisley and Renfrewshire South while his SNP opponent Mhairi Black urged people to "vote for a fresh start".

Liberal Democrat Equalities Minister Jo Swinson said it had been "a glorious start to polling day" in East Dunbartonshire.

Scottish Green MSP Alison Johnstone joined Edinburgh South Green candidate Phyl meyer at Marchmont St Giles polling station.

David Coburn MEP, Ukip's only elected politician in Scotland, also voted in Edinburgh before setting off for a round of broadcast interviews.

In response to the Scottish Conservative leader's claim, a police spokesman said: "Police Scotland is aware of the tweet from Ruth Davidson and is looking into the matter."

A spokesman for the Scottish Conservatives said: "Two members of the public complained to us regarding a situation at Newington Sports and Leisure Polling Station in Annan.

"We have passed on their complaint to the electoral registration officer at the council and have spoken to Police Scotland. We take all such reports seriously and always pass on the relevant information."

A spokesman for Dumfries and Galloway Council said: "Election staff and Police Scotland have been visiting polling stations across Dumfries and Galloway throughout the day to make sure that voters can vote and that campaigners are acting responsibly.

"Police officers have been speaking to campaigners as part of their checks at the polling stations. This was the case at the Annan polling station.

"Currently, no official complaints have been received."

Meanwhile, figures from some Scottish councils have shed light on the take-up of postal votes in parts of the country.

Around 80% of postal votes have been returned in Scotland's capital, Edinburgh Council said.

A total of 357,929 people are registered to take part in Edinburgh.

Sue Bruce, returning officer for the city, said: "We already have an 80% turnout for postal votes which I think demonstrates the interest in the election."

A total of 32,151 electors across the three Highland constituencies applied for postal votes, according to Highland Council.

This compares to 21,908 Highland applications for postal votes at the last general election held in May 2010.

In Ross, Skye and Lochaber 8,230 of 9,828 postal votes have been received (84%).

Caithness, Sutherland and Ross returned 7,292 of 8,900 postal votes (82%).

Inverness returned 13,330 out of 16,114 postal votes (83%) and Nairn returned 1,501 out of 2,110 postal votes (71%).

Dumfries and Galloway Council said there are 75,249 registered voters in the region, with 16,234 postal vote packs issued in the area.

The Dumfriesshire, Clydesdale and Tweeddale constituency has 68,483 registered voters and 14,056 postal votes were requested there.

"So far the returning officer advised that 85% of postal votes had been returned," a spokesman confirmed.