Amnesty International call on the Nigerian government to launch an inquiry after two days of clashes between Nigerian troops and a Shiite Muslim group in the northern city of Zaria last month. Despite the lack of official figures, talk on the ground is of 300, 400, 600 or more -- a huge number even in a region where at least 17,000 have been killed in Boko Haram's Islamist insurgency since 2009.