The death toll was likely to rise, according to Dr. Aisha Eisani, the spokeswoman for the Pakistan Institute of Medical Sciences where the dead and wounded were taken, said an AP report.
The hospital, reportedly, is also treating around 50 people who were wounded in the blast.
The explosion happened in the morning when shoppers were buying supplies at the market. According to the police, approximately five kilograms (11 pounds) of explosives were hidden in a fruit carton.
Explosions of similar kind are not new in Pakistani cities such as the northwestern city of Peshawar or the southern port city of Karachi, but rarely do such incidents occur in Islamabad.