Nippon Mitsubishi Oil Corp., the nation's largest oil firm, announced Wednesday that it will close its crude-oil processing facilities in Kawasaki, Kanagawa Prefecture, by the end of September to consolidate its refineries.

The move by the nation's No. 1 oil firm may trigger further facility consolidation by other companies, as Japan's oil industry is suffering from excessive production capacity.

Through the closure, Nippon Mitsubishi will reduce its daily capacity of crude-oil processing by 75,000 barrels. The firm's capacity currently stands at 1.37 million barrels. The firm will also reduce workers at the Kawasaki plant from 210 to 50, and the closure of oil-processing facilities will save about 9 billion yen a year, company officials said.

It will be the largest oil-processing plant to be closed after oil product imports were liberalized in April 1996.

Nippon Mitsubishi was created last week after Nippon Oil Co. and Mitsubishi Oil Co. merged to survive cut-throat competition, excessive capacity and falling gasoline prices. Industrywide daily production capacity -- some 5.3 million barrels -- is estimated to exceed domestic demand by 20 percent, according to industry sources.

The Kawasaki plant, which was owned by Mitsubishi Oil, is located close to Nippon Oil's plant in the Negishi district of Yokohama. The close location is considered to be one of the reasons for the closure of the smaller plant.