KINSHASA, Dec 10 (Reuters) - Burkina Faso"s President Roch Kabore on Friday nominated the former head of a nuclear-test-ban agency Lassina Zerbo as prime minister amid an escalating security crisis that has killed thousands and led to street protests. Under pressure to make changes, Kabore fired Prime Minister Christophe Dabire on Wednesday, the latest upheaval in a leadership shake-up which has included military top brass. Zerbo, a physicist who studied in Paris, Canada and the United States, lead the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization for eight years, stepping down in August. Burkina Faso is at the heart of an Islamist insurgency that has swept through large parts the arid Sahel region, killing thousands of people and forcing millions more from their homes. Despite efforts by former colonial ruler France and other regional armies, attacks continue unabated, leaving local communities vulnerable.