At least 11 people were killed when two female suicide bombers blew themselves up near an army camp in troubled northern Cameroon in an attack blamed on Boko Haram Islamists.

President Paul Biya condemned the "cowardly and odious" attack, which took place on Sunday, and said he had given "strict instructions to the defence and security forces to secure our country."

Northern Cameroon, like Nigeria, Chad and Niger, has been hit in bloody attacks by Boko Haram, whose insurgency has now expanded across the region from the militants' homeland Nigeria.

Sunday's explosions occurred 50 metres (yards) apart within a few seconds of each other, near a camp of Cameroon's Rapid Intervention Battalion in the border town of Fotokol which faces the Nigerian outpost of Gamboru.

A government statement said the victims included 10 civilians and a Chadian soldier. Seven others were injured -- four Chadian and three Cameroonian soldiers.

Cameroonian and Chadian troops are deployed in Fotokol under a joint offensive to fight Boko Haram.

"We heard a loud explosion. Initially we thought it was a shell fired from Nigeria by Boko Haram but it was a woman who blew herself up," the source said.

"Seconds later there was another similar blast at a spot about 50 metres away. I counted 12 bodies," the source said.

A Cameroonian police officer said the first explosion happened at the entrance to the camp and the second in a neighbourhood spot where locals gather to break their fast during the holy Muslim month of Ramadan.

Boko Haram's deadly insurgency has killed at least 15,000 people since 2009 and left more than 1.5 million homeless.

A four-nation coalition of Nigeria, Niger, Chad and Cameroon has reportedly pushed the militants out of captured towns and villages in an operation that began in February.

But the group has stepped up attacks since Nigerian President Muhammadu Buhari took power in May vowing to crush the insurgency.

Last week, the group claimed responsibility for twin suicide bombings in the Chadian capital N'Djamena in June that left 38 people dead.