It was the first bomb attack in nearly a month in Maiduguri, the birthplace of Boko Haram, whose six-year insurgency has killed about 20,000 people and driven 2.3 million others from their homes.

In Cameroon, Communications Minister Issa Tchiroma Bakary said four teenage girls with explosive devices strapped to their bodies crossed into the country from Nigeria on Saturday and were approached by self-defense civilian fighters in the border town of Fotokol.

"When a member of a local vigilante committee made to stop them, one blew herself up, killing five members of a family," he said. "On hearing the explosion, soldiers fired into the air to frighten [any attackers]. The three others panicked and detonated explosives tied round their bodies, but they only killed themselves."

In many recent attacks, bombers have detonated explosives when stopped for searches that have become routine in parts of Nigeria and Cameroon.

The routine searches and checkpoints now in place are believed to have prevented the recent attacks from killing even more people, police said.

Suicide attacks, village raids and kidnappings continue although Nigeria's military has reportedly destroyed scores of Boko Haram camps in recent weeks.

Al Jazeera and The Associated Press