The protests erupted in Nawa Kadal area in interior of the city when security forces were being withdrawn after poll duty, they said.
Bashir Ahmad Bhat, aged 24, was killed and Nazir Ahmad and Haleema were injured when security forces allegedly opened fire to restore law and order, the sources said.
Ahmad was hit by a bullet and was admitted in Soura Medical Institute in a critical condition.
Haleema, who suffered injuries in pellet fire, was being treated at SMHS hospital, the sources said.
The polling was by and large peaceful but as security forces were being withdrawn, stone-pelting incidents were reported from various parts of the city.