Seventy-one soldiers killed in Niger in country's deadliest attacks
While no group has claimed responsibilities for the killing, militant linked to the al-Qaeda and the self-styled Islamic State have carried out similar attacks across West Africa’s Sahel region this year.
A Nigerian ministry spokesman said in a televised statement that a "substantial" number of terrorists had been neutralised.
He added that 12 military personnel had been wounded and others were missing.
Niger President Issoufou Mahamadou cut short a visit to a peace and security conference in Egypt to return to Niamey, the country's capital.
The conference, now postponed to early 2020, would have seen him meet French President Emmanuel Macron, along with various Sahelian leaders, to discuss France's presence in the region and the fight against jihadist organisations.
Militant in cars and motorbikes stormed the outpost on Tuesday night, carrying explosives, RFI Afrique reported.
According to The Guardian, local media reported that the attackers, who remain unidentified, targeted communications equipment at the outpost, before launching an assault on its defences.
The fighting lasted a total of three hours. Artillery fire was combined with explosive-laden cares, used as kamikaze vehicles.
Nigerien forces are currently waging a battle with Boko Haram militants in the southeast border of the country, near Nigeria.
They are also fighting extremist aligned with Al-Qaeda and IS in the west near Mali and Libya.
Only on Monday, an army camp in the western Tahou region was attacked, with three Niger soldiers and 14 militants killed.
In October 2017, four US soldiers and four Nigerien soldiers lost their lives as a result of a militant ambush, in a village on 30 miles away from the site of Tuesday night's attacks.
The wide belt of poor, anarchic territory in West Africa is gripped by growing insecurity.
Despite the creation of a French-backed task force composed of Niger, Burkina Faso, Mali, Mauritanian and Chad, as well the deployment of 4,500 French troops, jihadi groups continue to step up their attacks in the region.
Late last month, IS claimed responsibility for provoking a collision of two military helicopters killing 13, bring the total of French troops killed in the Sahel region to 41.
The crisis in the region can be traced back to 2012, when northern Mali was overtaken by separatist militants.
This led to French military intervention to counter the insurgent activity. While a peace deal was signed in 2015, it was only partially implemented.
New groups have emerged across the Sahel region, which has seen a flood of weaponry from Libya after the death of Mummar Gaddafi.