(ANSA) - BELGRADE, AUG 13 - Four police officers were injured yesterday evening during anti-government protests in Vrbas and Backa Palanka. According to media reports, in both cases, officers formed cordons to separate protesters from conservative SNS activists guarding their party headquarters, led by President Aleksandar Vucic. Protesters pelted activists and officers with rocks, bottles, and other items. Belgrade authorities strongly condemned the violence. (ANSA).