At least 69 people, including a local mayor, have been killed in an attack in Niger's volatile "tri-border" zone with Burkina Faso and Mali, the interior ministry said on Thursday.
The assault took place on Tuesday at Adab-Dab, a village about 55 kilometres (32 miles) from Banibangou in the western region of Tillaberi, but was only confirmed by the government on Thursday.
"The mayor of the commune of Banibangou, while travelling with a delegation from the commune, was ambushed by unidentified armed bandits," the ministry said in a statement.
"The provisional toll of the attack... is 69 dead, including the mayor, and 15 survivors," it said.
A search was under way for the attackers. The government declared two days of national morning from Friday.
Local sources said earlier that a motorcycle-borne defence force was attacked by "heavily armed members of the ISGS (Islamic State in the Greater Sahara," who were also on motorbikes.
Another source said the target of the attack was a local anti-jihadist defence force called the Vigilance Committees, which was headed by the mayor of Banibangou district.
The assailants headed off back to Mali "taking the bodies of their fighters with them", the source said.
The defence force had recently been set up by local people following a string of attacks on farm workers in remote fields by highly mobile jihadists, a former mayor said.
The militia had set off for Adab-Dab on Tuesday to hunt for armed men who had been attacking villages and stealing cattle.
The world's poorest country by the benchmark of the UN's Human Development Index (HDI), Niger is facing jihadist insurgencies both on its western border with Mali and Burkina Faso and on its southeastern frontier with Nigeria.
The western insurgency began with incursions in 2015. The bloodshed escalated in 2017, with massacres carried out by groups affiliated to al-Qaeda and the so-called Islamic State.
Human Rights Watch estimated in August that more than 420 civilians had been killed since the start of the year in western Niger. In one incident alone, 100 people were killed in attacks on villages on January 2.
In March, 141 members of the Tuareg community were massacred in Tahoua, a vast desert region abutting Mali.
In September, President Mohamed Bazoum, making his first visit to the region since being elected in February, said the attacks on "unarmed innocent people" were a sign the jihadists were losing ground against the army.
But on October 20, 11 members of the National Guard and a gendarme were killed in an ambush on a regional prefect's motorcade in the Bankilare district.
The United Nations has meanwhile warned that the Tillaberi region is facing a "major food crisis", with almost 600,000 people exposed to food insecurity.
"Insecurity and recurrent attacks by suspected elements of non-state armed groups targeting farmers and civilians will have serious repercussions this year on the already precarious food situation," the UN Coordination of Humanitarian Affairs office warned in a report sent to AFP last month.