Boko Haram has been accused of deploying a wave of female bombers in recent months, including in Kano, and blame for the latest violence will likely fall on the Islamist insurgents.
Kano state police commissioner Adenrele Shinaba said the blast at the Kantin Kwari market in Kano city was "a twin suicide bombing carried out by two young girls in hijab".
"They came by the market and asked to be directed to a public convenience. The bombs detonated, killing them and four others," he told AFP. At least seven others were injured, he added.
He estimated that the attackers were in their late teens and said they were accompanied by a man who disappeared after the girls blew themselves up.
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Blood stained the walls and floors of affected buildings following the blasts. Angry youths converged on the area and were kept at bay by police and soldiers, an AFP correspondent said.
The bombers' remains were then taken away.
Kano, the key city in the mainly Muslim north, has been among the places hardest hit by Boko Haram's five-year uprising aimed at creating a caliphate in the region.
Boko Haram gunmen rampaged across Kano in January 2012, killing at least 185 people.
Last month's mosque bombing apparently targeted the influential Emir of Kano, Muhammad Sanusi II, who had previously called on citizens to take up arms against Boko Haram.
Sanusi was not at the mosque at the time of the attack but analysts said the Islamists may have been trying to send him a message after several previous assassination attempts against other Islamic leaders who spoke out against extremism.