* Tokayev certain to be confirmed as next president
* Enjoys backing of strongman ex-president Nazarbayev
* Nazarbayev effectively still in charge as national leader
* Police disperse hundreds of election day protesters (Adds exit poll data)
ALMATY, June 9 (Reuters) - Police in Kazakhstan detained about 500 people on Sunday after dispersing protests against an uncompetitive presidential election set to confirm Kassym-Jomart Tokayev as the successor to veteran leader Nursultan Nazarbayev.
Nazarbayev, who had run the oil-rich former Soviet republic for almost three decades before stepping down in March, and retains sweeping powers, hand-picked the 66-year-old diplomat to succeed him, making the outcome of the vote against challengers with little political profile all but certain.
Two exit polls published by local pollsters gave Tokayev about 70 percent of the vote.
Hundreds people chanting "Shame! Shame!" staged protests on Sunday in Almaty and Nur-Sultan, the capital city that was renamed after Nazarbayev at Tokayev's suggestion.
But a smooth transfer of power is positive news for neighbouring Russia and China, and for foreign energy and mining companies that have invested hundreds of billions of dollars.
For many of Kazakhstan's 12 million registered voters, Tokayev, the interim president and also a former prime minister, was the only familiar face among seven candidates in a brief and uneventful campaign.
"Well, Nazarbayev is no longer on the ballot and I don't know any of the other candidates," said Natalya, a pensioner, after casting her vote on Sunday for Tokayev.
PROTESTS DISPERSED
Nazarbayev, 78, who holds the official title of Yelbasy, or national leader, and continues to run the ruling Nur Otan party, routinely took over 90 percent of the vote in elections described by Western observers as neither free nor fair.
Kazakhstan's rubber-stamp parliament, whose upper chamber Tokayev chaired before assuming the presidency, is devoid of opposition, and dissent is largely stifled through control of traditional and electronic media and social networks.
Telegram, a popular mobile messaging app, was inaccessible on Sunday in Almaty, Kazakhstan's largest city, and Facebook was also blocked for hours early in the day.
Reuters correspondents in Almaty and Nur-Sultan saw police clad in riot gear detain dozens of demonstrators as they forcefully dispersed rallies. The Interior Ministry later said police had detained about 500 people, describing them as "radical elements seeking to destabilise society".