Sarajevo will mark 100 years since the assassination that sparked World War I, an act that still deeply divides the people of the Balkans over the legacy of that fateful day.

On June 28, 1914 a Bosnian Serb nationalist shot dead the Austrian Archduke Franz Ferdinand and his wife, setting off a chain of events that sucked Europe’s great powers into four years of violence unprecedented in its scale and intensity.

Many of the former foes marked the centenary on the sidelines of an EU summit on Thursday with a low-key ceremony at Belgium’s Ypres, where German forces used mustard gas for the first time in 1915.

But the deep Balkan divisions stirred up by the anniversary have made it impossible for heads of state and government to come together at the site of the assassination in the Bosnian capital.

Wildly differing interpretations of 20th-century history endure in a region where the scars of the wars that marked the break-up of Yugoslavia in the 1990s, unleashing centuries of resentment and divisions, are still fresh.

And a particularly divisive figure is the archduke’s assassin, the 19-year-old Serb nationalist Gavrilo Princip.

While the Muslim majority in today’s Sarajevo see Princip as a terrorist who unleashed calamity, the Serbs regard him as a hero seeking to liberate the Slavs from the Austro-Hungarian occupier.

Resenting the notion that Serb nationalism was to blame for triggering the Great War, Bosnian Serb leaders have refused to join the main Sarajevo commemorations that will feature a late afternoon performance by the Vienna Philharmonic, the symbolic envoy from the capital of a once-loathed empire.

Instead they will hold their own early afternoon ceremonies, unveiling monuments to Princip in a Serb area of Sarajevo as well as in eastern Bosnia and in Belgrade.