Gunmen killed 12 soldiers Wednesday in a predawn raid on a military base in southeastern Niger's Diffa region, a regular target of Boko Haram jihadists, the defence ministry said.
Another eight soldiers were wounded in the attack on the Blabrine military unit, said the ministry statement read out on state radio, adding that this was a provisional toll.
The attack was "very probably" carried out by Boko Haram, the statement added.
This was the latest in a string of increasingly brazen attacks near the west African country's border with Nigeria, where the radical Islamist insurgency has claimed hundreds of lives.
The attack was launched at around 3:00 am (0200 GMT), a municipal source told AFP earlier on condition of anonymity.
A senior official in Diffa added that military equipment had been torched in the attack.
Diffa, which borders the birthplace of Boko Haram in northeastern Nigeria, has been hit by repeated cross-border attacks by the Nigerian jihadist group since 2015.
There was a lull in the attacks late last year, but they have ramped up since March when 10 civilians were killed by a suicide bomber in the town of N'Guigmi, about 40 kilometres (25 miles) from the Blabrine base.
The mayor of Kabalewa, a village close to N'Guigmi, and his wife were kidnapped by Boko Haram members earlier this month.
The jihadist group has also previously carried out large-scale assaults on military posts, including a raid on a base near the southeastern town of Bosso in 2016 in which 26 soldiers were killed.
'Threat spreads to the south'
Boko Haram, loosely translated as "Western education is banned", wants to create a hardline Islamic state.
A regional military coalition is battling the group, but the decade-long insurgency has killed at least 35,000 people in Nigeria alone.
Located in the Lake Chad basin in the middle of the Sahel, the Diffa region is home to 120,000 refugees from Nigeria fleeing the Boko Haram violence, as well as 110,000 people internally displaced within Niger, according to UN data released this month.
The region has also seen flooding after heavy rains caused the Komadougou Yobe river to burst its banks, affecting at least 40,000 people, the government has said.
As well as facing Boko Haram to the southeast, Niger is also battling jihadists -- including those from the Islamic State group -- in the west near the Malian border.
Niger's President Mahamadou Issoufou has repeatedly called on the West and the United Nations to help the country battle the jihadists.
But the presence of French, American, and German forces in Niger as well as the UN in Mali has not stopped the increasing attacks.
"Not a day goes by without loss of life," Issoufou said last month, warning that the situation was urgent as "the threat spreads to the south".