Serbia's special war crimes court on Tuesday sentenced 14 former Yugoslav Army soldiers and paramilitaries to a total of 128 years in jail for the 1991 killings of 70 Croat civilians.

Belgrade - Serbia will vote for a new president and parliament on May 6 after Boris Tadic formally resigned on Thursday, bidding for re-election and to keep his pro-Western Democratic Party at the helm of a new, reformist coalition.

Tadic's resignation, which he announced 10 months early on Wednesday, sets up a showdown with the opposition Serbian Progressive Party (SNS), whose conservative, populist policies have played on voter anger over the state of the economy and corruption.

SNS leader Tomislav Nikolic, once a hardline nationalist who has since embraced integration with the West, will run against Tadic in a repeat of the last presidential election when Nikolic narrowly lost.

Tadic said a fresh mandate across the board was vital if the Balkan country was to prevent reforms at the heart of its EU membership bid from being derailed.

He formally resigned on Thursday. Parliament speaker Slavica Djukic-Dejanovic, who becomes acting-president, immediately set the presidential election for May 6, when the former Yugoslav republic was already due to vote for a new parliament.

Nikolic's party has a single-digit lead over the Democratic Party in most opinion polls, but 54-year-old Tadic is personally more popular than the party he leads.

The Democratic Party is banking on him to help it close the gap when voters cast their ballots.

“The focus will be on the presidential candidates far more than the parties,” said pollster Marko Blagojevic of the Centre for Free Elections and Democracy (CESID). “It's a dead-heat between the two biggest parties.”

The country of 7.3 million people became an official candidate for EU accession in March, more than a decade after the overthrow of Serb strongman Slobodan Milosevic.

Economic growth is stalling and unemployment has reached 26.7 percent as the entire western Balkans suffers from the fallout from the debt crisis in the euro zone, Serbia's main trading partner and investor. - Reuters