By Segun Owen

YENEGOA, Nigeria, Feb 21 (Reuters) - Gunmen ambushed a busload of football fans travelling to a match in southern Nigeria on Saturday and killed at least six in an apparent revenge attack, police and local officials said.

The supporters were travelling from Yenegoa in Bayelsa state to neighbouring Delta state. Local officials said the execution-style killing appeared to be in retaliation for a nightclub shooting in Yenegoa on Friday.

"The fans coming to Delta were ambushed and shot. Eight were killed and seven were injured and are in hospital," Delta state police spokesman Charles Muka said.

A senior Bayelsa state government official who visited the scene said he had seen six bodies being taken to the mortuary in the nearby town of Ughelli. Another local official put the death toll among the "Ocean Boys" football supporters at 13.

Bayelsa and Delta are two of the main states in Nigeria's restive Niger Delta, where criminal gangs and militant groups regularly ambush vehicles and carry out kidnappings for ransom.

The government official said the killings appeared to be part of a feud between rival "cults", a word often used in Nigeria to refer to university campus gangs originally sponsored by politicians to commit abuses at election time.

Detailed statistics are not available, but hundreds of people are believed to have been killed in clashes between such gangs since the early 1990s at the more than 100 federal and regional universities and polytechnics in Nigeria.

The lawlessness in a region which is home to Africa's biggest oil and gas industry has forced many foreign companies to remove expatriate staff and scale back their operations. (For full Reuters Africa coverage and to have your say on the top issues, visit: http://af.reuters.com/ ) (Writing by Nick Tattersall; editing by Robert Woodward)

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