Shinsei Bank has asked Sony Group Corp. to help counter a takeover bid by online financial firm SBI Holdings Inc., sources with knowledge of the matter said Wednesday.

If Sony agrees to become a so-called white knight, it would lead to a bidding war for Shinsei, which has strengths in the consumer loan and credit card businesses with some 3 million retail bank accounts.

Shinsei has yet to announce its position on SBI's unsolicited tender offer announced last week. But the sources said the bank is seeking friendly buyers, including Sony.