Both the United States and United nations have condemned the “horrendous” suicide bombing of worshippers at the Kano central mosque on Friday.
No fewer than 120 people died in the blasts and the gun attacks. About 270 people were also injured.
US state Department spokeswoman Jen Paski said the US “stands with the Nigerian people in their struggle against violent extremism”.
“These attacks, while as yet unclaimed, have all the hallmarks of Boko Haram and the group’s disregard for human life as it continues in its efforts to destabilize Nigeria, ” Paski said.
UN chief Ban Ki-moon condemned the attack and said “there can be no justification for attacks on civilians”.
The attack at the Grand Mosque in Kano, the biggest city in the mainly Muslim north of the country, came just as Friday prayers had started.
The mosque is attached to the palace of the Emir of Kano Muhammad Sanusi II, Nigeria’s second most senior Muslim cleric, who last week urged civilians to take up arms against Boko Haram.
The blasts came after a bomb attack was foiled against a mosque in the northeastern city of Maiduguri earlier on Friday, five days after two female suicide bombers killed over 45 people in the city.
National police spokesman Emmanuel Ojukwu told AFP that the bombers blew themselves up in quick succession then “gunmen opened fire on those who were trying to escape”.
Ojukwu said he did not know whether the suicide bombers were male or female, after a spate of attacks by women in recent months, and did not give an exact figure on the number of gunmen.
But he said an angry mob killed four of the shooters in the chaotic aftermath. Witnesses in the city said they were set on fire.
An AFP reporter at the Murtala Mohammed Specialist Hospital morgue counted 92 bodies, most of them men and boys with blast injuries and severe burns.
As night fell, hundreds of people were desperately trying to use the lights on their mobile phones to identify loved ones.
But a senior rescue official said later that there were at least 120 dead and 270 wounded. Emergency workers were still trying to visit all hospitals, he added.
The Emir of Kano last week told worshippers at the same mosque that northerners should take up arms against Boko Haram, which has been fighting for a hardline Islamic state since 2009.
He also cast doubt on Nigerian troops’ ability to protect civilians and end the insurgency, in rare public comments by a cleric on political and military affairs.
The emir, who is out of the country in Paris, France, is a hugely influential figure in Nigeria, which is home to more than 80 million Muslims, most of whom live in the north.