Kohlberg Kravis Roberts’ capital market unit, launched at the height of the buy-out boom two years ago, is raising its profile on Wall Street, and creating friction with investment banks in the process.

When KKR, the private equity group, founded its capital market unit, it insisted it would complement the Wall Street banks that had served as the group’s advisers and financiers. But as banks become more familiar with KKR Capital Markets, they are increasingly seeing it as a competitor, executives say.