BBC Hausa's Mansur Liman: After the explosions gunmen started shooting
Dozens of people have been killed in explosions during Friday prayers at one of the biggest mosques in the Nigerian city of Kano, reports say.
Many more people have been hurt, with one rescue official putting casualty figures at just under 200.
The Central Mosque is where the influential Muslim leader, the Emir of Kano, usually leads prayers.
The emir recently called for people to arm themselves against Islamist militant group Boko Haram.
The group has killed more than 2,000 people this year, rights groups say.
Some reports said there was gunfire in Kano after the explosions.
The rescue official, speaking to Agence France-Presse, put the casualty toll at 64 dead and 126 hurt, although this has not been independently confirmed.
One worshipper, Aminu Abdullahi, told the agency: "Two bombs exploded, one after the other, in the premises of the Grand Mosque seconds after the prayers had started."
He said the third blast was on a nearby road.
BBC Hausa editor Mansur Liman said one witness at a local hospital had described the scenes there as being the most horrible he had ever seen.
Our editor says Boko Haram will be the main suspects, as the attack bore all the hallmarks of the group.
'Call for anarchy'
The emir, Muhammad Sanusi, is currently in Saudi Arabia.
Reliable sources in the emir's palace told the BBC that he had arrived in Saudi Arabia late on Thursday night from Paris.
Boko Haram has targeted the city, the largest in northern Nigeria, several times during its five-year insurgency.
But most of its attacks are further east.
Earlier this month, the emir told a prayer meeting that people should "acquire what they need" to protect themselves.
A police spokesman said the emir's comments were a "call for anarchy" and should not be acted on.
The emir, who until earlier this year was governor of Nigeria's central bank, normally stays silent on political matters.
Source : bbc.com