PORTLAND – Banknorth Group Inc. announced Thursday it will buy Warren Bancorp Inc. and its six branches on Massachusetts’ north shore.

Banknorth said it would buy the company for $122.6 million in cash and stock. Warren Bancorp is the parent company of Warren Five Cents Savings Bank, which has four banks in Peabody, Mass., and one each in Beverly and North Beverly.

Banknorth operates as Banknorth Massachusetts in that state and has acquired Andover Bancorp, MetroWest Bank and Ipswich Bancshares in the past year.

“We continue to execute our plan of acquiring sound banking companies that extend and enhance our Massachusetts franchise,” said William Ryan, Banknorth chairman, president and chief executive officer.

As of June 30, Warren Bancorp had assets of $460 million, deposits of $394 million and loans of $345 million.

Banknorth, headquartered in Portland, is the parent of Peoples Heritage Bank in Maine and Bank of New Hampshire. It also operates banks in Connecticut, New York and Vermont.

The transaction is subject to regulatory approval and is expected to be completed by the end of the year.