The massacre that took place in the north-central village of Barsalogho on August 24 was one of the deadliest reported in the West African country, which has fought jihadist violence for a decade.

Although the government led by Captain Ibrahim Traore, who seized power in a 2022 coup, issued no official toll, some 400 mostly civilians were killed, according to a collective that represents victims' families.

"For us, the President is and will be the main culprit of the death of more than 400 relatives of ours. It is his fault they were killed," said the Justice Collective for Barsalogho (CJB) in a statement to AFP on Friday, and whose members spoke on condition of anonymity for security reasons.

Months before the attack, the junta chief personally asked security forces to "mobilise the population to dig trenches" in order to protect their villages, the collective previously said.

Civilians were forcibly enrolled in construction works on the city's periphery to defend Barsalogho against terrorist combat.

Gripping shovels and pickaxes, the population was massacred in the trenches they had been digging, videos shot by the attackers showed.

- 'Martyr city' -

Traore, 36, came to power vowing to swiftly regain control over a nation plagued by jihadist armed groups.

He has not commented on the Barsalogho killings, for which the Al-Qaeda-linked group Jama'at Nusrat al-Islam wal Muslimeen (JNIM) claimed responsibility.

"We have asked President Ibrahim Traore to acknowledge his responsibility and ask for the forgiveness of the sons and daughters of Sanmatenga," the province where the massacre took place, CJB said.

Traore's refusal to express his condolences "is a serious offence to the humanity and to the dignity of Barsalogho," CJB added.

"Barsalogho is a martyr city which will remain in the collective conscience of Burkinabes."

Criticism of Burkina Faso's strongman is rare, with dissident voices being arrested or disappearing.

Thousands have died and about two million have been displaced by fighting that has raged since 2015, when an insurgency spilled over into Burkina Faso from neighbouring Mali.

Burkinabe Prime Minister Apollinaire Joachimson Kyelem de Tambela on Wednesday called the Barsalogho events a "tragedy", without giving further detail.

The Citizen Coalition for the Sahel, which is made up of a dozen civil society NGOs, on Friday encouraged "the authorities to keep up their efforts to shed light on this tragedy, to look for, arrest and prosecute its perpetrators, in order to do the victims and their families justice".

Back-to-back coups in Burkina Faso, in January and September 2022, were precipitated by bloody attacks perpetrated by armed groups.

Jihadist fighters affiliated with Al-Qaeda and the Islamic State group have killed more than 20,000 people since 2015 -- including some 3,800 this year alone -- according to the ACLED analysis group, which tracks conflict.