Sovereign wealth funds have provided more than half the equity for the BlackRock fund that bought $15bn of troubled mortgage debt from UBS this month, people with knowledge of the matter say.

The BlackRock deal highlights the rapidly evolving strategies of the sovereign wealth funds, which initially sought to take advantage of the turmoil in global markets by investing directly in beleaguered financial institutions. However, these rescue financing deals led to fears of losses by the funds – and a political backlash in the West. This has led sovereign wealth funds to look for lower-profile opportunities, often by investing through private equity funds.