Nigeria: Gunmen attack Kano emir's convoy

                              The emir is revered in Nigeria - he met President Goodluck Jonathan after bombs in Kano a year ago

Nigeria gunmen have attacked the convoy of the prominent religious leader, the Emir of Kano.

The emir survived, but his driver and two guards were killed.

No-one has admitted the attack, but suspicion is bound to fall on the militant group Boko Haram, which has previously killed Muslim clerics.

The emir is highly revered by Muslims and the attacks have caused shock in northern Nigeria, says the BBC's Lagos correspondent, Will Ross.

Men on motorbikes and in a car opened fire on the emir's convoy as he was returning from a ceremony at a mosque.

"There was an unfortunate incident today. The emir's convoy was attacked by unknown gunmen as he was returning from Koranic graduation ceremony in Kano city, Kano state governor Musa Rabiu Kwankwaso told AFP news agency.

"Three people in his convoy were killed but the Emir is unhurt," he said.

Boko Haram gunmen have killed Muslim clerics before, including those who have spoken out against the group's campaign of violence, says our correspondent.

Emir al-Haji Ado Bayero - who is in his 80s - has been on the throne for almost 50 years and has been careful not to openly denounce the activities of the Islamist militants, he says.

Over the past two years, violence in northern Nigeria has escalated.

Boko Haram is fighting to overthrow the government and create an Islamic state.

The group has admitted being behind a number of attacks against churches and other establishments since 2009.

More than 600 people were killed last year in attacks blamed on it.

Human rights groups say that more than 3,000 people have been killed by Boko Haram since 2010.