Burkina has been caught since 2015 in a spiral of jihadist violence perpetrated by groups affiliated with Islamic State and Al-Qaeda, which were already hitting neighbouring Mali and Niger.

"A large number of Jama'at Nusrat al-Islam wal Muslimeen (JNIM) fighters attacked a military base, homes and Internally Displaced People's camps in the city Djibo, in the Sahel region, killing at least 40 civilians and injuring more than 42," the UN agency said.

The agency said attacks on civilians were "inexcusable and must stop" with those behind them apprehended and judged at a fair and independent trail.

It added that deliberate targeting of civilians constituted a "war crime."

Burkinabe security forces told AFP that jihadists had carried out a huge attack Sunday on an army post at Djibo and that the army had killed dozens of the attackers.

Thre security forces added soldiers had been killed but did not mention civilian casualties.

Djibo, near the border area straddling Niger, Burkina Faso and Mali, has been besieged by jihadist groups active in the region for months.

Several convoys seeking to resupply the town have been attacked.