At least 12 Cameroonian soldiers were killed Monday night in an attack by Islamic militants on the border with Nigeria, according to a statement from the Cameroonian Ministry of Defense.

The attack also left over a dozen soldiers wounded and occurred in the Lake Chad area near the town of Wulgo, the ministry said Thursday. While no group was initially blamed for the attack, officials later said it was suspected to have been carried out by extremists from the Boko Haram group or its breakaway faction that is loyal to the Islamic State group.

Pointing to Boko Haram militants, the ministry cited the “advanced weaponry they increasingly have at their disposal” and the “apparent alliance with powerful transnational criminal entities” as contributing factors to Monday’s attack.

Some 35,000 civilians have been killed, and more than 2 million have been displaced in northeastern Nigeria alone, according to the U.N. The 2014 kidnapping of 276 schoolgirls by Boko Haram in the village of Chibok in Borno state — the epicenter of the conflict — captured the attention of the world.

In January, at least 40 people were killed in an attack by Boko Haram across the border in Nigeria.