NIAMEY (Reuters) - The death toll from Thursday’s attack by suspected jihadists on a Niger army base has risen to at least 89, four security sources said, surpassing a raid last month that killed 71 soldiers as the deadliest against Nigerien forces in years.

The government said on Thursday that 25 soldiers were killed, according to a provisional death toll, while successfully repelling the attack in the western town of Chinagodrar by assailants aboard motorcycles and other vehicles.

Four security sources told Reuters that at least 89 members of Niger’s security forces killed in the attack were buried on Saturday in the capital, Niamey.

One of the sources said the actual death toll could be higher because a number of soldiers were buried immediately on Thursday in Chinagodrar.

Defence Minister Issoufou Katambe said that an updated death toll would be announced after a national security council meeting on Sunday.

The Chinagodrar attack, coming a month after the raid in nearby Inates by fighters from an Islamic State affiliate that killed 71 soldiers, highlights the deteriorating security situation near Niger’s borders with Mali and Burkina Faso.

Attacks have risen fourfold over the past year in Niger, killing nearly 400 people, according to data from the Armed Conflict Location & Event Data Project, a non-profit research organization, despite efforts by international forces to stop militants linked to Islamic State and al Qaeda.

French fighter jets were scrambled on Thursday to scare off the attackers, France’s regional taskforce said, possibly averting an even heavier casualty count.

No group has yet claimed responsibility for the attack, but Katambe said on Friday that the army would launch a new offensive against jihadists.

West Africa’s Sahel region, a semi-arid belt beneath the Sahara, has been in crisis since 2012, when ethnic Tuareg rebels and loosely aligned jihadists seized the northern two-thirds of Mali, forcing France to intervene to temporarily beat them back.