The worst affected countries were Burkina Faso and Mali, both riven by armed groups and led by officers who took power in military coups, an annual report published by the rights group said.

"Armed groups and government forces in West Africa have committed atrocities with impunity in 2024," the HRW report said.

Burkina Faso's army and volunteer fighters had killed at least a thousand civilians in the first half of 2024, HRW said, citing figures from conflict monitoring group ACLED.

Neighbouring Mali's security forces and their mercenary allies from Russia's paramilitary Wagner group were likewise responsible for "serious human rights violations against civilians as part of counterinsurgency operations against abusive Islamist armed groups".

Mali's armed forces and its allies were responsible for 1,021 civilian deaths between January 1 and October 11, said HRW, again citing ACLED figures.

That nearly doubled the toll from 2023, when 632 people died.

The Malian junta systematically denies any accusations of abuses by the army.

Meanwhile, the desert borderlands straddling junta-led Burkina Faso, Mali and Niger have become the scene of attacks by armed groups linked to the Islamic State and Al-Qaeda, the report added.

Niger's neighbour Nigeria has not been spared jihadist and army violence, with HRW reporting numerous kidnappings and murderous attacks on civilians by Boko Haram and its Islamic State-aligned splinter group, Islamic State West Africa Province (ISWAP).

The rights group also pointed to two air strikes carried out by the Nigerian army in December 2023 and September 2024, supposedly targeting "bandits" and which killed 85 and 24 people respectively.

"Civilians have borne the brunt of the fighting between government forces and armed groups," said Mausi Segun, Africa director at Human Rights Watch.

"The authorities in Nigeria and the Sahel used unchecked power to commit rights violations with impunity," Segun said.