Violence broke out when police tried to disperse thousands of members of the Islamic Movement in Nigeria (IMN) marching from Kano in Kano state, to Zaria in Kaduna state -- where they have been banned -- for the Ashura religious festival.
There have been several incidents of sectarian violence involving the IMN in the past year in Nigeria, with Sunni Muslim mobs attacking Shiite ceremonies just in recent weeks.
"I saw 15 bodies sprawled on the ground before the police evacuated them," he added of the violence in Kwanar Dawaki on the outskirts of Kano.
Witness Kabiru Mudassir said he saw more than "10 bodies being taken away in a police van."
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Nigerian police said they opened fire on the IMN crowd, who were armed with bows and arrows, after one of their officers was hurt.
"They injured one of our officers and our men opened fire because they were becoming violent," said a police officer who asked to remain anonymous.
"Shiite members armed with bows and arrows and some dangerous weapons killed one policeman and injured three others," Yusuf said. "Eight Shiite members were seriously injured. They were taken to hospital and were confirmed dead."
The violence comes just over a month since 10 IMN members -- who were also in the streets for religious celebrations -- were killed in the town of Funtua in northern Katsina state following clashes with security forces.
In October, Kano police banned IMN from conducting street processions ahead of the annual Ashura rites.