The blast struck the mosque in the village of Kouyape, in Kolofata district north near the Nigerian border, at around 5:30 am (0430 GMT) during morning prayers, a security source said.
Since July last year Cameroon’s far north has been hit by a series of attacks blamed on Boko Haram, which has pledged allegiance to the Islamic State group.
“Eleven worshippers were killed at the scene. A twelfth died of their wounds in hospital,” the security source said, adding that the attacker was praying alongside other worshippers when he blew himself up.
Another source close to the security services confirmed the blast killed 12 people and the bomber.
“The suicide bomber was praying with the others,” the source said, adding that the imam of the mosque figured among the victims.
The bombing came after two people were killed overnight in the same area in another attack blamed on Boko Haram, the security source said.
Cameroon has beefed up its military presence along the Nigerian border as part of a regional coalition, after years of doing little to stop Boko Haram fighters using its territory as a rear base to arm and equip themselves.
Since late November the Cameroon army has carried out operations in several border areas aimed at weakening Nigerian jihadists who have been very active in the region.
Sources say these operations have significantly weakened Boko Haram’s capability, forcing the insurgents to turn away from direct confrontations with the military in favour of suicide attacks.
Boko Haram in the past year stepped up cross-border attacks in Niger, Chad and Cameroon while also continuing to mount shooting and suicide assaults on markets, mosques and other mostly civilian targets within Nigeria itself.
The group’s six-year campaign for a hardline Islamic state in northeast Nigeria has killed at least 17,000 people and made more than 2.6 million others homeless.
Despite the offensives launched by regional forces, the group maintains strongholds in areas that are difficult to access, such as the Sambisa forest, the Mandara mountains and the numerous islands of Lake Chad.