Nigerian President Goodluck Jonathan has vowed to "not leave any stone unturned" in tracking down the terrorists who attacked a mosque, killing more than 80 worshippers and wounding at least 100 others.
Jonathan issued a statement Saturday urging Nigerians "not to despair in this moment of great trial" in the nation's history, and "remain united to confront the common enemy."
A series of explosions followed by gunfire outside the crowded central mosque in Kano struck just after the start of Friday prayers.
Witnesses say they saw scores of people wounded and feared dead after two bombs exploded in a courtyard outside Kano's Grand Mosque, and a third detonated nearby.
Police arrived on the scene to confront an angry mob of youths yelling and brandishing sticks and stones. Police struggled to gain entrance to the mosque.
A VOA reporter says the mood eased after that, as medical authorities tended to the wounded.
The U.S. State Department called the attack "horrendous" and condemned it in the strongest terms. It said the United States stands with the Nigerian people in their struggle against violent extremism and the threat of terrorism, and affirms its ongoing commitment to work with all Nigerians to combat these atrocities.
A spokesman for U.N. Secretary-General Ban Ki-moon said the U.N. chief "calls on authorities to swiftly bring the perpetrators to justice."
The mosque is associated with one of the country's most influential Muslim authorities, the emir of Kano, who recently called for Nigerians to take up arms against the militant group Boko Haram. The emir is currently out of the country.
No one has claimed responsibility for the bombing in Nigeria's second largest city, but suspicion is likely to fall on Boko Haram, which has carried out similar attacks.
Kano is a city of more than 3 million people in the northern part of Nigeria.