Alhaji Muhammadu, 60, was shot by two men riding on motorcycles as he left a mosque in the Hoton Fulani area of the mainly Muslim northern city. He died in hospital.

"We had just finished our evening prayers and he was heading home when two men on motorcycles stopped close to him and shot him twice before they drove off," resident Maikudi Danlami told AFP.

"They were from all indication members of Boko Haram because after shooting him they said, 'let's see how you are going to be critical of us. Let's see what your boasting can achieve," said Danlami, who witnessed the shooting.

A nurse at a local hospital said Muhammadu "was shot twice at close range."

Residents said that Muhammadu was known for openly criticising Boko Haram, who have claimed a series of attacks in Kano, including a January 20 assault that killed at least 185.

"He never hid his aversion to Boko Haram and would voice his disapproval of the sect publicly," said Hasan Kawu, another resident.

The Boko Haram insurgency has already claimed more than 200 lives this year. The Islamists have largely struck at the police and other symbols of authority, but Christians have also been targeted.

In a leaflet distributed around Kano last month, Boko Haram said it would target anyone who "collaborates" against the group, "even if he is a Muslim."