People leaving church after a Sunday service in a village near Bauchi, Nigeria, September 2010 (World Watch Monitor)

At least 16 people were killed as gunmen opened fire at churchgoers returning from a midnight service on New Year’s Eve in Omuku, a town in Nigeria’s southern Rivers state.

According to the BBC, the New Year’s Eve fireworks initially made it difficult for people to realise that shots were being fired and people were being killed.

Rivers state is Nigeria’s main oil-producing region and, according to local reports, the incident was linked to growing tensions between rival gangs, who demand a greater share of oil revenues.

Omuku, which is around 85km from the state capital, Port Harcourt, has a history of violent crime but had enjoyed a period of relative peace after the government introduced an amnesty for former gang members – but this amnesty has “lapsed” in the past year, according to the BBC, resulting in more violence.