The west African country of Niger says an insurgent attack on a military base killed 89 soldiers.

Fierce fighting broke out between soldiers and Islamist militants at the base near the border with Mali on Thursday.

The government initially put the death toll among its soldiers at 25, but revised the figure upward on Sunday. It also says 77 militants were killed.

The clash came after an attack on another base left about 70 soldiers dead last month. The government declared three days of national mourning starting Monday.

Niger is one of the countries in the Sahel, a region south of the Sahara Desert.

The area is seeing the rise of Al-Qaeda, Islamic State militants and other Islamist groups.

The United Nations says terrorist attacks claimed more than 4,000 lives in the Sahel last year.

NHK