WARRI, Nigeria (AFP) - An explosion rocked the southern Nigerian oil city of Warri on Monday during a ceremony to mark an amnesty for former rebel fighters, an AFP correspondent reported.

The device went off near the main hall where the event was taking place, sending large plumes of smoke into the air. It was not immediately clear whether anyone was injured.
The blast went off moments after the region's main armed group MEND threatened to detonate three devices it had planted near the venue.
Top officials and community leaders were gathered at the ceremony.