West African leaders have pledged $1 billion to combat the spiraling threat of Islamist militancy in the region, the head of the regional ECOWAS bloc said on Saturday.

Groups with links to al-Qaida and Islamic State have strengthened their foothold across the arid Sahel region this year, making large swaths of territory ungovernable and stoking local ethnic violence, especially in Mali and Burkina Faso.

The fifteen members of the West African bloc and the presidents of Mauritania and Chad had gathered for an extraordinary summit in Burkina Faso’s capital, Ougadougou, to address the growing insecurity.

ECOWAS Commission President Jean-Claude Kassi Brou said the commission had decided to “contribute financially and urgently to joint efforts in the fight against terrorism” by pledging $1 billion.

In a speech following the closed meeting, Brou also called on the United Nations to strengthen its MINUSMA peacekeeping mission, which has been based in Mali since 2013.

In July, the U.N. said Islamist attacks were spreading so fast in West Africa that the region should consider bolstering its response beyond current military efforts.

In 2017, five countries — Burkina Faso, Niger, Chad, Mali and Mauritania — backed by France, launched the G5 Sahel task force to combat the insurgents. But the initiative has been perennially underfunded.

The situation in Burkina Faso has deteriorated in particular in recent weeks. An attack in late August killed 24 soldiers, one of the heaviest losses yet in the nation’s fight against Islamist militants. Last week, 29 people were killed in separate attacks in its troubled central-northern region.

Once a pocket of relative calm in the Sahel, Burkina has suffered a homegrown insurgency for the past three years, which has been amplified by a spillover of jihadi violence and criminality from its chaotic neighbor Mali.

Large swaths of Burkina’s north are now out of control, and France’s military Sahel mission began limited operations there earlier this year.