* Former ultra-nationalist to become PM
* Centre-right promising economic overhaul
* Serbia setting out on talks on joining EU (Updates throughout)
By Ivana Sekularac and Matt Robinson
BELGRADE, March 16 (Reuters) - Serbia's centre-right Progressives, a party of former ultra-nationalists converted to the cause of European Union membership, won an outright majority in parliament on Sunday promising deep economic reform.
The margin of victory, rivalling the results of late strongman Slobodan Milosevic during the war years of the 1990s, will see Progressive Party (SNS) leader Aleksandar Vucic become prime minister as Serbia embarks on talks to join the EU.
Pollster Cesid said the Progressives had won 48.8 percent of ballots cast, which under Serbia's electoral system would translate into around 157 seats in the 250-seat parliament. The party itself said it had won 49.3 percent.
"No one has had such a day," Vucic told cheering supporters in Belgrade. "My goal is not to be rich, my goal is for the people of Serbia to live better," he said.
Vucic has promised root-and-branch reform of Serbia's bloated public sector, pension system and labour law in order for the country - the most populous to emerge from the ashes of federal Yugoslavia - to claim its place as an economic leader in the Western Balkans.
The party is expected to move quickly to secure a new precautionary loan deal with the International Monetary Fund.
Analysts said the SNS owed its victory to Vucic's personal popularity as the face of an anti-crime drive that has struck a chord with many Serbs angry at decades of deep-rooted graft.
Critics, however, are unnerved at the power amassed by a man who up until five years ago was a virulent anti-Western disciple of the Greater Serbia ideology that fuelled the wars of Yugoslavia's bloody demise in the 1990s.
Vucic, 44, was information minister in the late 1990s when newspapers were fined and shuttered under a law designed to muzzle dissent as Milosevic led Serbia into war with NATO over Kosovo.
He says he made mistakes, and has learned from them.
"I'm not ashamed to change my bad habits and characteristics. On the contrary, I am proud."
OPPOSITION ROUTED
According to Cesid, the Socialist Party of outgoing Prime Minister Ivica Dacic came in second with 14 percent.
The opposition was routed, with the Democratic Party - the main opposition force to Milosevic which held power from his 2000 ouster until 2012 - taking around 6 percent. The party saw its political base split by the defection of former Serbian president Boris Tadic, whose new party also took around 6 percent. Turnout was around 53 percent.
Analysts say Vucic may seek to bring Tadic into the government.
The SNS forced the snap election after just 18 months in coalition government with the Socialists, saying it needed a stronger mandate to overhaul Serbia's shaky finances.
The country of 7.3 million people must commit to rein in its budget deficit and public debt in order to secure a new loan deal with the IMF, which could come soon after a new government is formed.
"The political establishment and the population appear ready/primed for reform, and a new strong government with a fresh mandate has no excuse now for not reforming," Timothy Ash, head of emerging markets research at Standard Bank, said in an email ahead of the election.
The outgoing government, in which Vucic was deputy prime minister, clinched the start of EU membership talks in January, shortly before the coalition collapsed.
The talks were reward for a landmark deal under which Serbia agreed to cede its last foothold in the country's former Kosovo province, which declared independence six years ago and has been recognised by more than 100 countries.
The EU accession process, likely to run beyond 2020, should help steer reform and lure much-needed foreign investment. Serbia is a natural hub for a region with deep linguistic and cultural ties.
"I voted for Vucic because he's doing the right thing," said 68-year-old pensioner Ceda Kerkez after voting in the capital.
"He's not in bed with the tycoons, he's arresting the tycoons, and I think there will be more arrests after the election." (Editing by Robin Pomeroy)
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