Dozens have been killed in a gun and bomb attack 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 been waging an insurgency in Nigeria since 2009 and has killed more than 2,000 people this year, rights groups say.
‘Helter-skelter’
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.
Three explosions were reported in and around the mosque. The attackers also turned gunfire on worshippers.
One eyewitness told the BBC’s Focus on Africa: “The imam was about to start prayer when he saw somebody in a car trying to force himself into the mosque. But when people stopped him, he detonated the explosions. People started running helter-skelter.”
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.
Analysis: Tomi Oladipo, BBC Africa security correspondent, Lagos
It is clear it is not only Christians who face the threat of violence in northern Nigeria. This is a major mosque, frequented by one of the country’s most influential Muslim leaders, Kano’s emir.
Emir Muhammad Sanusi II has criticised Boko Haram and only last week urged civilians to take up arms against the group. This has raised questions as to whether he was the target of today’s attack – although he was out of the country at the time.
While violence in remote rural areas is no longer news for many Nigerians, the increasing attacks in larger cities are sending shockwaves across the country. The military’s ongoing counter-terrorism efforts will need more concrete results to boost public confidence.
Our editor says Boko Haram will be the main suspects, as the attack bore all the hallmarks of the group.
No-one from the group has yet commented.
Boko Haram has stepped up attacks against civilian targets since the Nigerian military launched an offensive last year.
Boko Haram was also behind the kidnapping of more than 200 schoolgirls from Chibok in Borno state this year, an act that sparked international outrage.
Who are Boko Haram?
- Founded in 2002
- Initially focused on opposing Western education – Boko Haram means “Western education is forbidden” in the Hausa language
- Launched military operations in 2009 to create Islamic state
- Thousands killed, mostly in north-eastern Nigeria – also attacked police and UN headquarters in capital, Abuja
- Some three million people affected
- Declared terrorist group by US in 2013
Source: BBC