The attack happened in the village of Dakasoye, some 20 kilometres south of the city, during a march by followers of the Islamic Movement of Nigeria.
The group, led by Sheikh Ibrahim Zakzaky, said on its website the blast happened at 2:00 pm (1300 GMT) and that "scores" had been killed.
But there was no official indication of casualties and one of the organisers told AFP: "It's a huge crowd so it's too early to give a precise figure of casualties.
The organiser, who asked to remain anonymous, said the bomber ran into the crowd before he could be spotted and detonated his explosives.
More From This Section
"He was dressed in black like everyone else. His accomplice was initially arrested and confessed they were sent by Boko Haram," he added.
"They were part of the young men abducted by Boko Haram in (the Borno state town of) Mubi last year and taken to Sambisa Forest where they were given some military training.
"They were sent to Kano 11 days ago and kept in a house specifically for this attack."
Boko Haram, the radical Sunni jihadists who want to create a hardline Islamic state in northeast Nigeria, has previously been blamed for attacks on Shia Muslims in the region.
Last November at least 15 people were killed and some 50 others injured in a suicide bombing targeting the Shia Muslim festival of Ashura in the city of Potiskum, in Yobe state.
In April, a suicide bomber targeted a group of Shiite Muslims outside an open-air mosque, also in Potiskum. He killed himself and wounded three worshippers.
The followers were on a "symbolic trek" from Kano to Zaria, in neighbouring Kaduna state, where Zakzaky is based, to mark the 40th day of Ashura.
Their arrival on December 3 is designed to coincide with the gathering of pilgrims at Hussein's tomb in the Iraqi city of Karbala.
Today's attack came after a female bomber killed eight in the northeastern city of Maiduguri last Sunday and four teenage girls blew themselves up in northern Cameroon on Saturday killing five.