The army in Burkina Faso now says more than 50 soldiers were killed in an attack by presumed Islamist militants in the north on Friday.
It said in a statement that 51 bodies had been found so far, several soldiers were still missing and three wounded soldiers had been evacuated from the scene.
The military had said earlier on Monday that eight had died in what it described as intense fighting in Oudalan province.
It said it had killed more than 100 of the assailants, though that number has not been independently verified.
This year has seen an upsurge in fighting in northern Burkina Faso, with more than 100 deaths reported in the first six weeks.
The failure to stem the bloodshed led to two coups last year and the ending of the French military mission to the country.
This incident was reported as France officially marked the end of its military operations in the country where its have been based since 2015 to help fight militants.