World Bulletin / News Desk

At least 13 people have been reportedly killed in violence in Nigeria's oil-rich Rivers State after gunmen opened fire on locals for "revenge".

"The violence started on Wednesday when a man killed a local chief over disagreement on royalties from an oil company in the area," Dandi Emmanuel, a youth leader from the area, told Anadolu Agency on Thursday night.

"The whole thing degenerated into some sort of gang war as youths loyal to the deceased launched a counter offensive that resulted into about 13 deaths overnight," he said.

Another source, who asked not to be named, said the clash was "a cult war and the violence was between two rival cult gangs from Egite and Akabta communities" in the Ogbia/Egbeme/Ndoni local government area.

"In all, over 13 lives were lost and properties were also destroyed. The gunmen who invaded the communities didn't spare their opponents' house either," he added.

However, Rivers police chief Rotimi Ogunshakin confirmed to AA that only eight people died in the clashes.

Rivers state, though now relatively calm, was the epicenter of gang wars linked to political rivalry and violent oil militancy and piracy between 2006 and 2009 during which many lives were lost and oil installations damaged.