FRANKFURT (Reuters) - German insurer Allianz (>> Allianz) said it had agreed to sell its 90 percent stake in private bank Oldenburgische Landesbank (OLB) (>> Oldenburgische Landesbank AG) to U.S. private equity firm Apollo (>> Apollo Global Management LLC) for 300 million euros (264.2 million pounds).

Apollo, which is consolidating the northern German banking market and has also signalled interest in HSH Nordbank, said it would attach OLB to its Bremer Kreditbank, which it bought in 2014.

Allianz, which announced the sale agreement on Friday, had said last September it was exploring options for OLB, Germany's largest regional private bank by assets. It acquired OLB as part of Dresdner Bank in 2001 and had said was no longer of strategic importance.

New EU capital rules at the start of last year have been prompting insurers such as Allianz to review whether the profit they gain from stake holdings is worth the regulatory capital they are required to hold.

Apollo will make an offer to the other 10 percent of OLB shareholders. The price it is paying Allianz represents 14.30 euros per share, compared with OLB's closing price on Friday of 18.30 euros per share.

Allianz said it would continue to cooperate with OLB to distribute insurance.

(Reporting by Georgina Prodhan and Alexander Huebner; Editing by Tom Brown)