Bands of Muslim youths armed with cutlasses and clubs burned houses and set up roadblocks to kill minority Christians to avenge the slaying of hundreds of Muslims by Christians in central Nigeria last week.
A witness, Jackson Kentebe, described seeing at least 24 bodies lying on the streets in two districts of town, some burned and others bearing knife wounds to the head.
Police used live ammunition on rioters to restore order.
"I had to give the shoot on sight order as the killing and mayhem was getting out of hand," said police commissioner Ganiyu Dawodu.
He confirmed 30 people had died in the last two days, including 25 on Wednesday, but a senior security source said at least twice that number had been killed.
"If Kano people cannot tolerate us, we should be given six months to vacate. We can no longer be living in perpetual fear in a place our safety is not guaranteed"
Shortly before the riot started on Tuesday, Islamic elders gave the government an ultimatum to protect Muslims in the central Plateau state (where hundreds were killed by Christian militia in a land dispute last week) or face more violence.
Survivors of the attack on the remote farming town of Yelwa said they buried 630 corpses after a two-day assault by heavily armed militia.
It was not possible to verify the figure independently but police said "hundreds" were killed.
The OPEC oil exporting country of 130 million people is split equally between Muslims and Christians and has seen more than 6000 killed in religious violence in five years since democracy returned in 1999.
A leader of the Christian minority in Kano, an Ibo chief called Boniface Ibekwe, said Christians would prefer to leave than live in perpetual fear.
"If Kano people cannot tolerate us, we should be given six months to vacate," he said. "We can no longer be living in perpetual fear in a place our safety is not guaranteed."
Nigeria's Islamic leaders were outraged by the government's failure to prevent the Yelwa massacre, despite warnings from local Muslims that an attack was imminent.
Sectarian warfare has plagued
Nigeria in recent years
Muslims in Kano, 400 km north of the capital Abuja and the centre of Islamic activism in Nigeria, feel a strong bond with kinsmen in Plateau state who are mostly of the same Hausa-Fulani ethnic group.
People of the Tarok and other predominantly Christian tribes in Plateau accuse the Hausa-Fulani of invading their ancestral land and the Islamist groups of wanting to drive them out of the state.
But the semi-nomadic Hausa-Fulani say their families have grazed cattle there for generations.
The Yelwa massacre was the latest outbreak of a conflict dating to 2001 when more than 1000 died in religious and ethnic fighting in the state capital Jos. At least 1000 have been killed in the past three months.