Sumitomo Mitsui Financial Group is increasing its stake in Jefferies Financial Group Inc., as the two banks merge their equity operations in Japan following four years of deepening cooperation.

The two companies announced in a joint statement on Friday that Japan's second-largest bank, Sumitomo Mitsui, will raise its shareholding in the U.S. investment bank Jefferies from the current 15% to approximately 20%, while its voting rights will remain below 5%. Sumitomo Mitsui stated it plans to pay 135 billion yen ($912 million) for the additional shares.

The Tokyo-based bank will provide Jefferies with approximately $2.5 billion in new credit facilities for collaborative ventures in areas such as structured financing in Europe and the United States. The two companies have also agreed to establish a joint venture in Japan to conduct equity research, sales and trading, and equity capital markets business.