The United Nations envoy for West Africa and the Sahel says the region has experienced "a devastating surge in terrorist attacks against civilian and military targets" in recent months.

Mohamed Ibn Chambas told the UN Security Council on Wednesday that the "unprecedented terrorist violence" had shaken public confidence in the region.

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He said attacks have increased five-fold in Burkina Faso, Mali and Niger since 2016 with more than 4,000 deaths reported in 2019 compared with an estimated 770 deaths three years before.

In Burkina Faso, deaths rose even more dramatically from about 80 in 2016 to more than 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 UN envoy said 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.

Among the latest attacks was a rocket attack on Thursday on a base in northern Mali's restive Kidal region that wounded 20 people, including 18 UN peacekeepers, according to the UN spokesman in Mali.

Residents and a military source told the Reuters news agency that about 20 soldiers were killed and nearly 1,000 people made homeless on Tuesday evening in an attack on a town in Borno state in northeastern Nigeria.

Another one was Monday's roadside bombing in Mali's central region of Alatona, near the border with Mauritania, that left at least five soldiers dead. More than 140 Malian soldiers have been killed in armed attacks since September.

On Saturday, a roadside bomb attack in Burkina Faso also killed 14 people, including seven children and four women.

On Christmas Eve, 35 civilians, mostly female, were killed following an attack on a military outpost in Burkina Faso's northern Soum Province.

Chambas said governments, local "actors," regional organisations and the international community are mobilising to respond to the violence 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 November ISIL fighters attacked a hotel in Mali's capital and largest city, Bamako [File: Jerome Delay/AP]

In a report to the Security Council in late July, UN 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 of Iraq and the Levant (ISIL, also known as ISIS) and al-Qaeda armed groups were collaborating to undermine fragile countries.

Chambas said the attacks were also often intertwined with organised crime and violence among competing groups.

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

In the months ahead, he said, six West African countries will choose leaders in democratic elections.