At least seven members of Beninese security forces and five rangers working with a conservation nonprofit have been killed in an attack by an armed group in Benin’s National Park W that is overrun by militants, according to the conservation group.

The attack earlier this week on Wednesday happened not far from the Mékrou River in the 10,000-square-kilometer (3,800-square-miles) park which straddles the borders with Burkina Faso and Niger, the African Parks group said in a statement on Saturday.

Authorities in Benin have not yet spoken about the attack, which is common with the government and the military.

It is the latest in a surge in violence in which jihadis from the conflict-battered Sahel region that is south of the Sahara Desert have spread further into West Africa, targeting coastal states like Benin.

It was not clear which jihadi group carried out the attack in Park W, into which militants from troubled neighbors Burkina Faso and Niger have recently moved, raising fears they could use its vast protected area as a base for infiltrating other West African countries.

The al-Qaida linked JNIM group has been the most active in the Sahel and most recently in coastal West African states like Benin and Togo.

Although they were once believed to be spreading to the coastal states for better cover to recuperate, get financing and gather weapons to launch more attacks on Sahel governments, their fighters have started to attack communities and security forces as militancy begins to take root.