PORTLAND – Banknorth Group Inc. has announced that its board of directors has authorized the repurchase of up to 4 million shares, or about 3 percent, of the company’s common stock. Shares will be repurchased from time to time in open market transactions as, in the judgment of management, market conditions warrant.

The company recently repurchased 625,000 shares of its common stock. Banknorth Group, with headquarters in Portland, is one of the country’s 50 largest commercial banks with $18.5 billion in assets. Its Maine subsidiary is Peoples Heritage Bank.