Vandals in France damaged a sculpture of an Algerian military hero who resisted France's colonisation of the North African country, hours before it was to be inaugurated on Saturday. The lower part of the steel sculpture in the town of Amboise, where Emir Abdelkader was imprisoned from 1848 to 1952, was damaged in the attack which took place in the midst of an election campaign dominated by immigration and Islam. Amboise mayor Thierry Boutard said he was "ashamed" of those responsible and decided to proceed with the ceremony. "I was ashamed that someone would treat an artwork and an artist in this way," he said. "My second sentiment is, of course, one of indignation. This is a day of harmony and unity and this kind of behaviour is unspeakable." Police said they were investigating the incident. The sculpture by contemporary artist Michel Audiard was commissioned to coincide with the 60th anniversary of Algeria's independence. The sculpture of Abdelkader, an Islamic scholar who turned military leader and was feted as a hero in France for his defence of Christians in the Middle East, looks across the Loire river at the castle where he was imprisoned. Algeria's ambassador to France Mohamed Antar Daoud, who attended the inauguration, condemned the attack as an act of "unspeakable baseness" and said he was confident that the process of reconciliation between the two countries would endure. Ouassila Soum, a 37-year-old French woman of Algerian background who attended the inauguration, said the vandalism left her "with a knot in my stomach". "It's a shame and yet it's not surprising with the rhetoric of hate and the nauseating current atmosphere," she said. Called "France's worst enemy" in the late 19th century, Emir Abdelkader is considered one of the founders of modern-day Algeria. The rebellion he led failed, and he surrendered to French forces who shipped him to France, where he and his family spent four years under guard in Amboise castle. He later moved to Syria, where he won international acclaim for defending Christians during sectarian attacks. He was awarded the Legion of Honour, France's highest award for his role in trying to end the persecution.