Voters in Niger cast ballots in the country's first-ever presidential run-off Sunday, with incumbent Mahamadou Issoufou on track for a second term as the opposition observed a boycott.

The election pits 64-year-old Issoufou, a former mining engineer nicknamed "the Lion", against jailed opposition leader Hama Amadou, 66, known as "the Phoenix" for his ability to make political comebacks.

Increasingly targeted by jihadist fighters roaming its remote northern desert, and Nigeria's feared Boko Haram insurgents on its southern flank, Niger fears the emergence of its own brand of home-grown Islamist trouble.

In recent years foreign-funded aid groups and social media have brought ideas peddled by Wahhabism -- an ultraconservative form of Islam -- to more and more of Niger's 19 million people, one of the planet's poorest nations.

Voters in Niger went to the polls Sunday in an election in which President Mahamadou Issoufou has promised a "knockout" blow to his opponents, one of whom is behind bars on baby-trafficking charges.

A vast nation endowed with an abundance of uranium, gold, coal and oil but among the poorest on the planet, Niger is electing a head of state, as well as a new parliament, with Issoufou hoping for a second five-year term.

At least six Niger soldiers were killed on patrol when their vehicle hit a mine in the Diffa border region used by neighboring Nigeria's Boko Haram militants, local authorities and media said on Monday.

"An army vehicle ran over a mine causing deaths and injuries but we do not have the exact figures," Abari El Hadj Daouda, the mayor of the town of Kabalewa where the incident happened on Saturday, told AFP.

Niger's government has "foiled" a coup plot, resulting in a number of arrests, President Mahamadou Issoufou said in an address broadcast on national radio and television Thursday, adding that the situation was "under control".

The announcement came after local media and social media reports on Monday said at least four senior military officers had been arrested, information that was not immediately confirmed by the Niger authorities.

Violent clashes in Niger Monday between police and students protesting for better study conditions left at least seven injured and led to 79 arrests, the governor of the capital Niamey said.

Hundreds of college and high school students demonstrated in the city and clashed with police in the afternoon, an AFP journalist said.

An alleged Boko Haram attack on a village in southeastern Niger killed two of the country's soldiers, the Nigerien army said Friday, the latest deadly raid by the Islamist group.

The incident occurred when a nearby military unit was warned that an attack was imminent against the village of Baroua, near the border with Nigeria, at around 10:30pm (2130 GMT) on Thursday, and dispatched soldiers to the scene, according to a defense ministry statement read on state television.

Fifteen civilians were killed in an attack by Boko Haram militants on a border village in southeastern Niger, state television reported Friday, the latest deadly raid by the Islamist group.

The attack followed two months of calm in the area and took place as Muslims marked Eid al-Adha, the Feast of Sacrifice, the most important holiday of the Islamic calendar.

Algeria, Niger and Chad on Sunday stressed the urgency of creating a national unity government to solve the conflict in their neighbor Libya.

Algeria's African affairs ministers and the foreign ministers of Niger and Chad stressed the importance of such a government "to preserve Libya's unity and territorial integrity and its people's cohesion."

At least four people have died and more than 20,000 have been affected by floods in Niger caused by weeks of heavy rain, the United Nations said Friday.

The bad weather has destroyed 2,170 homes and flooded nearly 545 hectares of agricultural land, the U.N.'s Office for the Coordination of Humanitarian Affairs (OCHA) said in a statement.