DOUALA, Cameroon (Reuters) – Suicide bombers targeting a town in northern Cameroon killed 28 people and wounded 65 on Monday, one of the worst attacks yet in the Central African nation as it struggles to contain an overflow of violence blamed on Nigeria’s Boko Haram.

State-owned radio and local officials said four explosions struck a busy market and entrances to the town of Bodo, which borders the Islamist insurgency’s strongholds in northeastern Nigeria.

“The new toll is 28 dead and 65 wounded. Currently the situation is stable. Our security forces are in place,” said one official, who asked not to be named.

While there was no immediate claim of responsibility for the attack, northern Cameroon has become the scene of increasingly frequent suicide attacks as Boko Haram has stepped up cross-border violence that has also spread into Chad and Niger.

Twelve people were killed in an attack on Jan. 13 at a mosque in the town of Kouyape.

Bodo, separated from Nigeria by only a small border river, was previously targeted at the end of December when two female suicide bombers blew themselves up at the town entrance.

Boko Haram has killed thousands of people and driven more than 2 million people from their homes during its six-year insurgency in one of the world’s poorest regions.

Regional armies mounted an offensive against the insurgents last year that ousted them from many positions in northern Nigeria.

In the wake of that operation, Nigeria, Chad, Niger, Cameroon and Benin pledged to set up a 8,700-strong regional force tasked with wiping out Boko Haram. The United States has also sent troops to supply intelligence and other assistance.

The establishment of the force has been plagued by delays, however, and joint operations have yet to begin, leaving it up to national armies to tackle Boko Haram individually.

In the absence of effective coordination, security sources have warned this can often mean that soldiers just drive the militants across each other’s borders.

(Reporting by Josiane Kouagheu; Writing by Makini Brice and Joe Bavier; Editing by Edward McAllister and Mark Heinrich)