Seven election workers were killed early Sunday in Niger’s troubled western Tillaberi region when their vehicle hit a mine, the area’s governor told AFP.

The blast also injured three of the workers, who included the heads of polling stations, Tidjani Ibrahim Katiella told AFP.

The accident came as Niger holds a presidential election runoff between frontrunner Mohamed Bazoum, loyal to outgoing president Mahamadou Issoufou, and former president Mahamane Ousmane.

The team had been sent by the Tillaberi branch of the National Independent Electoral Commission (CENI) to monitor the polling, the governor said.

The explosion occurred in the town of Dargol some 100 kilometres (60 miles) from Niamey in the so-called tri-border region where Niger, Mali and Burkina Faso converge.

The vast and unstable region has been under a state of emergency since 2017.

It was the scene of one of the worst civilian massacres suffered by the Sahel country in early January, when around 100 people were killed during an attack on two villages.

The twin attack occurred on the day election officials announced results from the first round of the presidential vote held on December 27.(AFP)