One of the worst massacres in Burkina Faso's history has provoked a fierce public outcry from victims' relatives and religious leaders, piling pressure on the ruling junta of a country where spiralling insecurity has already stoked coups.

Islamist militants gunned down scores on Aug. 24 as residents of the north-central town of Barsalogho dug defensive trenches on the orders of the army, according to a group of affected families and an eyewitness account.

The ensuing carnage appears to be the deadliest single attack in the West African country since groups linked to al Qaeda and Islamic State first spread from neighbouring Mali around 2015.

Military authorities who seized power in 2022 have been tight-lipped. Junta members told state television on Aug. 25 that civilians and military personnel were killed, but did not provide a death toll.

The priest of the Archdiocese of Ouagadougou, a prominent member of the Catholic community, condemned the junta's response on Monday.

"To persist in silence and inaction is to contribute to the extinction of humanity in the heart of every human being," Father Jean Emmanuel Konvolbo said in a statement.

Pope Francis expressed deep sorrow for the "horrific acts" over the weekend.

A group of victims' relatives says at least 400 people died. They have issued a string of statements, calling out the junta under the anonymous banner of Justice Collective for Barsalogho (CJB) for fear of retribution, civil society sources say.

The group has accused authorities of "gagging those who dare to speak out about the tragedy."

It said soldiers tried to kidnap a volunteer fighter in Barsalogho on Thursday over audio recordings that denounced the attack.

Civilians who intervened managed to prevent his abduction, but an activist in the nearby city of Kaya, also linked to the recordings, went missing on the same day, it said in a statement on Saturday.

The junta did not respond to a request for comment.

A source in Kaya who knows the activist said his family has had no news since two plainclothes officers detained him at a cafe.

The source, who used to work in Barsalogho and is in contact with people there, said soldiers surrounded the town after the attack and were preventing residents from talking about what happened.

Barsalogho is one of several towns under jihadist blockade. Residents who leave risk being killed or kidnapped, and only military convoys can travel up the road linking it to Kaya, about 40 km (25 miles) south.

While some injured victims were evacuated to Kaya and elsewhere after the attack, the rest of the population remains stuck.

"The idea is to keep people in place," said the source, who did not wish to be named due to safety concerns.

'BREAKING POINT'

Junta leader Ibrahim Traore has become increasingly intolerant of critics since he ousted his predecessor Paul-Henri Damiba, who had himself toppled Burkina Faso's last elected president months earlier.

Both the 2022 coups stemmed in part from frustrations about authorities' failure to stem the Islamist violence. Like neighbouring military-led Mali and Niger, Burkina has cut ties with Western allies and turned to Russia for security support.

Yet violence has worsened significantly under Traore, analysts and humanitarian workers say.

Meanwhile, dozens of civil society activists, journalists, opposition politicians and even magistrates have been abducted, tortured and conscripted for speaking out against the junta, rights groups and Reuters have found.

The severity of the Barsalogho attack could stoke further dissent among both the army and civilians, analysts say.

"Even with Traore's coup-proofing measures, there are only so many embarrassing mass casualty events like this one that his regime can withstand," said Constantin Gouvy, a conflict researcher at the Clingendael Institute.

"If violence continues to spiral, there will be a breaking point," he said. "At some point the army and the population are bound to seek leadership change again."