DAKAR, Senegal (AP) — Amnesty International says Boko Haram has killed at least 60 people in a "devastating" attack on the northeastern Nigeria border town of Rann.

The international rights group has tweeted satellite imagery of the town, which it says shows hundreds of burned structures.

It says the attack on Monday by extremists who arrived on motorbikes left much of the town in flames.

Tens of thousands of people have fled attacks in Rann, near the border with Chad, in recent weeks.

The attacks come amid what Nigeria has called an extremist resurgence in recent months, posing a serious challenge for President Muhammadu Buhari as he seeks re-election in two weeks' time.