Polling is under way in Serbia's presidential elections, with Aleksandar Vucic hoping to tighten his grip on power amid opposition accusations he is shifting the country to authoritarian rule.

Vucic, the 47-year-old prime minister, is hoping to clinch more than 50 percent of the ballot in Sunday's poll, winning a five-year mandate as president outright.

Most surveys tip Vucic for an easy victory in the face of a divided opposition. But if he fails to win a majority in the first round, a second round runoff will be held on April 16.

The post of president has largely been ceremonial in recent times, but analysts believe it would be a much more influential position if occupied by Vucic.

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Vucic has touted economic success since becoming prime minister in 2014, achieving growth of 2.8 percent last year and cleaning up public finances.

But the average Serbian earns a mere $355 a month while unemployment is running above 15 percent.

The opposition has been unable to field a single candidate to run against him, so Vucic faces a wide range of challengers.

There are 10 opposition candidates bidding for president, including former ombudsman Sasa Jankovic, ex-foreign minister Vuk Jeremic and ultranationalist Vojislav Seselj.

And shaking up the race is Luka Maksimovic.

He campaigns in a Borat-style white suit, sports a samurai-style ponytail and hipster beard, touts a manifesto studded with lunatic pledges and uses a made-up name that mocks politics as the circus of greed.

Using the fictional name of Ljubisa Preletacevic - nicknamed "Beli" (White) - he could even come second in the race behind Vucic, some analysts say.

Vucic's one-man rule

Opposition candidates have presented the vote as a referendum on Vucic, whom they accuse of trying to consolidate power for himself.

Ultranationalist Seselj argues that "all the power should not be concentrated in the hands of a single man, Aleksandar Vucic".

Some voters echoed this position.

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"I cannot deny that Vucic works a lot, that he is a friend with both the West and Russia. But I do not want all the power to be in the hands of one politician any more," said 59-year old taxi driver Mihajlo.

But Katarina Markovic, a 73-year old retired lawyer, said it was important to support Vucic, whose reforms "provided results".

The progress made by the Vucic government "is already not bad. It should continue faster in the same direction," she told AFP news agency.

Both the opposition and independent media monitoring groups have cried foul over the omnipresence of Vucic in the media.

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In the week leading up to the vote, national TV channels devoted 51 percent of their airtime to Vucic, more than all the other candidates put together, according to analysis by the Kliping research agency published in the Danas daily.

That rose to 67 percent when his appearances as prime minister were taken into account, added the analysis.

On Thursday, the last day of the campaign, all but two of the dozen or so national dailies appeared wrapped in full-page ads reading: "On April 2, give a decisive vote to Aleksandar Vucic".

Political analyst Boban Stojanovic said he "wonders if, after such a campaign, the elections could be free and fair".

"I am not really sure. Such media domination is enough to make us wonder if the elections are fair," Stojanovic said.

Some 6.7 million eligible voters can cast their ballot from 7:00am (05:00 GMT) to 8:00pm. The first results are expected before midnight.