Gunmen fired at buses carrying minority Muslim voters on Saturday as Sri Lankans elected a new president, with the powerful Rajapaksa clan eyeing a comeback seven months after Islamist extremists staged deadly bombings.

But election chief Mahinda Deshapriya said over 80 percent of the 15.99 million electorate was estimated to have turned out Saturday, compared to 81.5 percent at the previous presidential poll in 2015.

"Comparatively this is the most peaceful presidential election we have had in this country," Deshapriya told reporters at the end of the 10-hour voting period.

Socio-economic profile of Sri Lanka, ahead of November 16 presidential election. Socio-economic profile of Sri Lanka, ahead of November 16 presidential election. Photo: AFP / Janis LATVELS

However, two women voters were injured when unidentified attackers pelted stones at their bus in the northwest region of Medawachchiya, police said.

The victims were travelling in a convoy of busses which had come under gunfire in the same region earlier in the day.

Sri Lanka's polls opened at 0130 GMT and security was tight with 85,000 police on duty Sri Lanka's polls opened at 0130 GMT and security was tight with 85,000 police on duty Photo: AFP / ISHARA S. KODIKARA

In the first attack, assailants burned tyres on the road and set up makeshift roadblocks before shooting at and pelting with stones two busses in a convoy of more than 100.

In the Tamil-dominated northern peninsula of Jaffna, meanwhile, police said they arrested 10 men they suspected of "trying to create trouble", while also complaining that the army had illegally set up roadblocks that could stop people getting to polling stations.

Such tactics are nothing new in Sri Lanka, which emerged from a horrific civil war only a decade ago. At the 2015 election, there was a series of explosions in the north.

Just under 16 million people are eligible to vote, with a record 35 candidates, including two Buddhist monks but just one woman Just under 16 million people are eligible to vote, with a record 35 candidates, including two Buddhist monks but just one woman Photo: AFP / Jewel SAMAD

Supporters from rival parties meanwhile clashed in a tea plantation area 90 kilometres (55 miles) east of the capital Colombo, with two people taken to hospital with cuts, the election commission said.

A Buddhist monk shows his inked finger after casting his vote A Buddhist monk shows his inked finger after casting his vote Photo: AFP / Jewel SAMAD

Some 85,000 police were on duty for the election with a record 35 candidates running for president, an office with considerable power similar to the French political system.

Just under 16 million people are eligible to vote, with a record 35 candidates, including two Buddhist monks but just one woman, on the monster ballot paper Just under 16 million people are eligible to vote, with a record 35 candidates, including two Buddhist monks but just one woman, on the monster ballot paper Photo: AFP / Jewel SAMAD

Results could come as early as midday (0630 GMT) on Sunday if there is a clear winner, but Deshapriya said floods in three out of the 22 electoral districts had disrupted counting and warned of delays in releasing the final tallies.

One of the two frontrunners is grey-haired retired army lieutenant colonel Gotabaya Rajapaksa, 70, younger brother to the charismatic but controversial Mahinda Rajapaksa, president from 2005-15.

Dubbed the "Terminator" by his own family, "Gota" is promising an infrastructure blitz and better security in the wake of the Islamist attacks in April that killed 269 people.

"Gotabaya will protect our country," construction worker Wasantha Samarajjeew, 51, said as he cast his ballot in Colombo.

His main rival is Sajith Premadasa, 52, from the governing liberal United National Party (UNP), son of assassinated ex-president Ranasinghe Premadasa.

He is also pushing development and security as well as free sanitary pads for poor women, earning him the nickname "Padman" after a famous Bollywood movie.

The Rajapaksas are adored by Sri Lanka's Sinhalese majority for defeating Tamil Tiger separatists and ending a 37-year civil war in 2009.

They are detested and feared by many Tamils, who make up 15 percent of the population. The conflict ended with some 40,000 Tamil civilians allegedly killed by the army.

During Mahinda Rajapaksa's presidency, Gotabaya was defence secretary and effectively ran the security forces, even allegedly overseeing "death squads" that bumped off political rivals, journalists and others.

He denies the allegations.

What also concerns Western countries, as well as India, is that strategically located Sri Lanka moved closer to China under Mahinda Rajapaksa, even allowing two Chinese submarines to dock in Colombo in 2014.

Mahinda says credit was unavailable elsewhere.

Western capitals "should give a fair chance to us", Basil Rajapaksa, another brother, told reporters. "They can't be monitors of this country. They must be partners."