Benin's government has admitted that 54 soldiers were killed by suspected jihadists in the country's north last week near the borders with Burkina Faso and Niger.

The authorities had previously said that only eight soldiers were killed.

The revised figure makes it the deadliest known attack since insurgents began operating in northern Benin at the beginning of the decade.

The attack has been claimed by an al-Qaeda-linked group - Jama'at Nusrat al-Islam wal Muslimeen, (Jnim), which is based in Mali but has in recent years expanded its operations to neighbouring countries.

The jihadist group had said it killed 70 soldiers in raids on two military posts in the north, according to intelligence group SITE.

Jnim is one of several jihadist groups operating in West Africa's Sahel region, especially Mali, Niger and Burkina Faso, where the military governments are struggling to contain the insurgency.

Benin and Togo have seen a rise in jihadist activity in recent years, as groups linked to Islamic State and al-Qaeda spread to the south.

"Heavy losses for the nation," wrote presidential spokesman Serge Nonvignon in a Facebook post on Wednesday.

Another government spokesperson, Wilfried Leandre Houngbedji, said that Benin was determined to continue the fight against the jihadists.

"We won't give in... I can assure you that sooner or later, sooner or later, we will win," he said.