* PM Fico, businessman-turned-philanthropist Kiska win 1st round
* Vote closer than polls showed, run-off on March 29
* Some voters wary of giving too much power to Fico's party (Adds details, quotes)
By Jason Hovet
PRAGUE, March 16 (Reuters) - Slovak Prime Minister Robert Fico and political newcomer Andrej Kiska won the most votes in the first round of a presidential election on Saturday, setting up a run-off that will either cement the ruling party's power or usher in an independent.
A Fico victory in a second-round vote on March 29 would give his centre-left Smer party full control of all the main power centres, even if the Slovak constitution does not grant the president himself a huge political role.
Fico, who has led the central European country since sweeping a parliamentary election in 2012, won 28 percent of the vote to Kiska's 24 percent on Saturday, a smaller margin than opinion polls had indicated.
Kiska, a 51-year-old businessman-turned-philanthropist, has seen his chances grow with voters worried over giving Fico too much power. The Smer party already has a parliamentary majority and runs the government without the need of a coalition.
Fico would have to give up his post of prime minister if he wins, but his party would replace him with a Smer nominee.
Fico, 49, took Slovakia into the euro zone in 2009 and has kept the country of 5.5 million friendly to investors despite levying extra taxes on banks and utilities.
The president has the power to name or approve some of the main figures in the country's prosecution and judicial branches, and this right has led to political clashes in the past.
Rule of law is a key concern for investors.
Slovakia has lured big foreign manufacturers such as carmakers Kia and Volkswagen, which have helped keep growth at decent levels even as others in central Europe slipped into recession amid the euro zone crisis.
Analysts say Fico, the favourite going into the election with a 9-15 point lead in most opinion polls, would be tempted to increase the powers of the presidency if he wins.
"He is a man of unlimited ambition," political analyst Grigorij Meseznikov said before the vote. "If he has the strength in parliament, the next day he will want to change the constitution (to get more powers)."
KISKA AS UNDERDOG
This worry has lifted Kiska, who made millions of dollars in consumer credit companies which he sold a decade ago before starting a charity to help families with ill children.
"The president must be non-partisan, independent, so the government has a healthy counterbalance," he told Reuters in an interview last week.
Slovak voters have shown before they can unite behind an underdog. Outgoing president Ivan Gasparovic was elected for the first of two five-year terms in 2004 because voters united against former authoritarian prime minister Vladimir Meciar.
Kiska is also riding a wave of popular anger over sleaze and distrust in established parties, something seen last year in the neighbouring Czech Republic, where an anti-graft movement of billionaire Andrej Babis, also a political newcomer, won the second most votes in an election.
But analysts also say Kiska lacks a clear political vision, and Fico has denied he would seek more power, campaigning instead on his experience as prime minister for six years, including leading the government in 2006-10.
If he wins in two weeks, a possible choice to succeed him is Robert Kalinak, the interior minister and longtime member of the party that Fico founded. (Additional reporting by Jan Lopatka; Editing by Lisa Shumaker and Paul Simao)