Mohamed Ibn Chambas told the U.N. Security Council Wednesday that the "unprecedented terrorist violence" has shaken public confidence.

He said terrorist attacks have increased five-fold in Burkina Faso, Mali and Niger since 2016 with over 4,000 deaths reported in 2019 compared to an estimated 770 deaths in 2016. In Burkina Faso, deaths rose even more dramatically from about 80 in 2016 to over 1,800 in 2019, he said.

"Most significantly, the geographic focus of terrorist attacks has shifted eastwards from Mali to Burkina Faso and is increasingly threatening West African coastal states," Chambas said.

The U.N. envoy said terrorist attacks are often "deliberate efforts by violent extremists to capture weapons and trafficking routes" and engage in illicit activities including illegal mining that sustain their operations.

He said governments, local "actors," regional organizations and the international community are mobilizing to respond to terrorism and violent extremism across West Africa and the Sahel.

Chambas urged leaders in the region to follow through on pledges to tackle terrorism, saying now "is the time for action."

In a report to the Security Council in late July, U.N. experts said "the most striking international developments" during the first six months of 2019 included "the growing ambition and reach of terrorist groups in the Sahel and West Africa" where fighters from Islamic State and al-Qaida are collaborating to undermine fragile countries.

The experts, who monitor U.N. sanctions against both extremist groups, said: "The number of regional states threatened with contagion from insurgencies in the Sahel and Nigeria has increased."

They said: "A sharp rise in violence and recruitment efforts in West Africa, motivated by Islamic State or al-Qaida affiliates, has been exacerbated "by porous borders and authorities ill-equipped to confront the growing threat."

Chambas said terrorism is also often intertwined with organized crime and violence among competing groups.

With close to 70 percent of West Africa's population dependent on agriculture and livestock-rearing, he said, clashes between farmers and herders "remain some of the most violent local conflicts in the region."

"Climate change, among other multiple factors, is increasingly exacerbating farmer-herder conflicts," Chambas said. "The impact of climate change on security also spawns a negative relationship between climate change, social cohesion, irregular migration and criminality in some places."

The U.N. envoy stressed that "stakes are high in the region this year, both in terms of security and political developments." In the months ahead, he said, six West African countries will choose leaders in democratic contests.