Major refiners Idemitsu Kosan Co. and Showa Shell Sekiyu K.K. each won approval from their shareholders Tuesday for their long-delayed merger plan, clearing the last hurdle for the April creation of a new oil industry giant.

At their respective extraordinary meetings, the companies' shareholders gave the green light to the April 1 integration of Idemitsu, Japan's second-largest oil wholesaler, and fourth-ranked Showa Shell.

Once the merger takes place, the country's oil wholesale sector will be dominated by industry leader JXTG Holdings Inc. and the newly merged firm.