Tokyo - Nippon Oil Corp, Japan's largest refiner, and Nippon Mining Holdings Inc on Thursday announced merger plans set to create the world's eight-largest oil company.

The two companies said a principal agreement has been reached to merge into a joint holding in October 2009. The aim of the merger, which would put their combined sales at about 13.15 trillion yen (about 140 billion dollars) was to improve competition in view of slower demand and falling prices, they said.

Nippon Minings is Japan's biggest copper producer and the country's sixth-largest refiner. (dpa)