Police rained tear gas on crowds and several demonstrators and riot police were injured in the southern Tunisian city of Gabes as thousands of people marched Wednesday to protest worsening air pollution from a phosphate-processing plant. The protest descended into clashes with police who attempted to disperse protesters trying to reach the plant in an industrial complex, which is a designated military zone. Gabes, home to more than 400,000 residents, lies at the heart of Tunisia’s phosphate industry, one of the key sources of export revenue for the North African country. Report by Lilia Blaise and Hamdi Tlili.