MAIDUGURI, Nigeria — A tragic error in a Nigerian Air Force operation targeting extremist rebels has left more than 100 civilians, including children, dead after an airstrike hit an active weekly market in the country’s conflict-battered northeastern region, multiple sources including a leading global rights group and local media confirmed Sunday. The incident has reignited longstanding concerns about the heavy human cost of Nigeria’s 12-year counter-insurgency campaign in the Sahel.