Officials say the death toll could climb after militants, who arrived on motorbikes and in cars, attacked a military base in the Gao region.
The latest fighting between the soldiers and militants took place in Tillaberi region, near the borders of both Mali and Burkina Faso.
Nigeria's military said attacks by militants from Boko Haram and a splinter group affiliated with Daesh had "necessitated the contiguous nations of the Lake Chad basin to jointly launch this massive onslaught."
Nigerians hurried to stock up on food and supplies after president Muhammadu Buhari’s announcement imposing a 14-day lockdown on Lagos city
Several opposition parties had called for the long-delayed parliamentary election to be postponed due to the Covid-19 pandemic, which has seen 18 people test positive since the country's first case was diagnosed earlier this week.
The memo from Army headquarters outlines plans to protect government food storage from looters as Africa’s most populous nation braces for the illness to spread further in the country.
Insurgents fired rocket-propelled grenades at a lorry carrying troops as it travelled near Gorgi village in Borno state, two military officers said without giving their names.
Opposition parties and civil society organisations have called for fresh protests on Monday and Tuesday after the African nation held a disputed referendum that critics say is a ploy to keep the president in power.
President AlphaConde is proposing a change to the constitution to codify gender equality and introduce other social reforms.
A fire that broke out in a suburb of Lagos has killed at least 15 people and injured several others. The cause of the explosion was not known.
In a nation dominated by Afrobeats, the 26-year-old who calls herself the "Nigerian Rock Goddess" is trying to change long-held perceptions that rock is something alien to her country's music scene.
Local sources said a "major" attack had killed soldiers who were hospitalised in Diffa, but they did not give figures.
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