A series of loud explosions rocked Nigeria's second city of Kano on Monday, residents said, describing at least four blasts in the Sabon Gari neighbourhood, which has been previously targetted by Boko Haram Islamists.

"There is confusion all over the place. There were four huge explosions, so huge that they shook the whole area. Everywhere is enveloped in smoke and dust," said Chinyere Madu, a fruit vendor.

The blasts were said to have targetted Enugu street in Sabon Gari, a strip filled with outdoor bars and eateries.

Resident Kola Oyebanji said he believed "beer parlours" were the target.

"My house is not far from there," he told AFP. "All my windows are shattered."

Kano is the largest city in Nigeria's mainly Muslim north, but Sabon Gari is a mostly Christian neighbourhood.

The cause of the blasts was not immediately clear, with police and emergency officials in Kano not available to comment.

Boko Haram, the extremist group which has said it is fighting to create an Islamic state in northern Nigeria, was blamed for coordinated suicide blasts at a bus park in Sabon Gari in March that killed at least 22 people.