Two female suicide bombers have attacked a mosque in a town near Cameroon’s border with Nigeria, killing at least 10 people and wounding about a dozen others, the governor of the region said.

The attack during morning prayers in the town of Kolofata on Wednesday is believed to have been carried out by members of the Islamist group Boko Haram who crossed the border into Cameroon a few days ago, said Midjiyawa Bakari.

Kolofata in Cameroon’s far north has been attacked repeatedly by Boko Haram.

Another suicide bombing in Cameroon blamed on the group in December killed at least seven people and wounded 30 others, officials said. In September, suicide bombers killed nine people in Kolofata and wounded 18.

Boko Haram began stepping up its attacks early last year on Cameroon and other countries that have supported the Nigerian military’s effort to crush the extremists.

The group’s six-year insurgency has killed about 20,000 people and displaced 2.3 million, according to Amnesty International and the United Nations.