Shinsei Bank said Friday it will launch defensive measures against an unsolicited takeover bid by Japanese online financial firm SBI Holdings Inc. and hold an extraordinary shareholders meeting to seek approval for the plan.

The decision by the bank's board marks a further flare-up in tensions, effectively making a tender offer launched a week ago by SBI hostile.

As part of its defense, Shinsei plans to issue new shares to existing shareholders to dilute SBI's shareholdings, a tactic known as a poison pill to foil the online financial firm's abrupt takeover attempt.