Nigeria , Africa 's top producer , has been forced to curb its output by 500,000 barrels a day , or about 20 percent of the country 's usual total , because of violence in the Niger Delta since the beginning of the year .
Africa /location/location/contains Nigeria
NNP , NNP POS JJ NN , VBZ VBN VBN TO VB PRP$ NN IN CD NNS DT NN , CC RB CD NN IN DT NN POS JJ NN , IN IN NN IN DT NNP NNP IN DT NN IN DT NN .
Africa
LOCATION
Nigeria
LOCATION
/location/location/contains