Tunis (AFP) - Thousands of Tunisians, led by their president and joined by several foreign dignitaries, are to march in the capital Sunday to denounce terrorism after the museum massacre of 22 tourists.On March 18, two gunmen targeted the National Bardo Museum in an attack claimed by the Islamic State group, dealing a severe blow to a country that was the cradle of the Arab Spring and is highly dependent on tourism.The dead tourists were from Italy, Japan, France, Spain, Colombia, Australia, Britain, Belgium, Poland and Russia.A Tunisian policeman was also gunned down.