Monacan investment fund Sovereign Asset Management has purchased an equity stake of more than 5 percent in UFJ Holdings Inc., making it the biggest single shareholder in Japan's fourth-largest banking group.

It is the first time that a foreign investor has become the biggest shareholder in one of Japan's top-four banking groups.

Sovereign Asset Management said in a statement that it has no plans to raise its stake in UFJ Holdings at the moment. It said its investment in UFJ Holdings is intended for long-term holdings.