Serbia's pro-Western President Boris Tadic has won re-election in a contest with nationalist Tomislav Nikolic, but his narrow victory may only have set up a fresh struggle over the country's future course.

Analysts say it puts the survival of Serbia's ruling coalition in question as it braces for the secession of Kosovo, the Albanian-dominated province, which has Western backing for a declaration of independence in the next few weeks.

Tadic won Sunday's presidential election by 50.5 percent to around 47.8 percent, according to a partial count by the state electoral commission, which reported many spoiled ballots. Tadic enjoys support of Belgrade and other major cities while his opponent is backed by provinces.

"Serbia has shown its great democratic potential," Tadic said, in his victory speech, praising Nikolic for "the number of votes he has won." "This is Serbia's victory. I think we have proven both to Europe and everywhere else in the world what kind of democracy we have in Serbia."

In a 2004 presidential race, Tadic beat Nikolic easily by some 9 percentage points, in what the West saw as a welcome sign that the reactionary nationalism which fuelled war in the 1990s over the breakup of Yugoslavia was steadily weakening, Reuters reports.