Five West African leaders have called upon the international community to help combat militant Islamists following the killing of 71 soldiers in Niger.

Niger's President Mahamadou Issoufou said the militants had become "professionals in the art of war."

The Islamic State (IS) group said it killed the soldiers during an attack on a military base in western Niger.

The soldiers were buried on Friday inside a military base close to the capital Niamey.

The leaders held a short prayer service beside the graves of the soldiers.

They included President Issoufou, and the leaders of Burkina Faso, Chad, Mali and Mauritania – the G5 Sahel nations bearing the brunt of attacks by militants linked to IS and al-Qaeda.

Last week's attack in Niger's western town of In Ates was described as the deadliest raid against the Nigerien military in living memory.