Herbert Smith Freehills and Norwegian firm Arntzen de Besche have advised Japanese trading house Mitsui on its 575-million-euro ($631 million) investment in Mainstream Renewable Power, a company controlled by Norway's Aker Horizons.

Norwegian firm BAHR represented Aker Horizons. Other law firms supporting the transaction include Vilaf in Vietnam and PJS Law in the Philippines.

With the investment, Mitsui will have a 27.5 percent stake in Mainstream, a global renewable energy project operator and green technology company. Mitsui's investment and global business network will help Mainstream speed up expansion of its portfolio of wind and solar energy in the Americas, Africa, Asia-Pacific and Europe, Reuters reported.

The Arntzen de Besche team was led by partners Per Dagslet and Henrik Braavold Johansen, while the Herbert Smith team was led by the firm’s global head of energy, Lewis McDonald, who was supported by partner Brigette Baillie.

The BAHR team was led by partner Stig Klausen Engelhart, who was supported by technology practice head Lars Kristian Sande.