Kohlberg Kravis Roberts has become the latest private equity firm to run the slide rule over Avaya, after the US telephone equipment maker's shares leapt 15% on reports of an approach from another bidder.

An industry source said KKR could be interested in the company as it sold Tenovis, a German portfolio company, to Avaya in 2004. Avaya paid $635m, including debt, for Tenovis to give KKR more than eight times its money.