First Niagara Financial Group Inc. will buy both HSBC branches in Fairfield and four other outlets in Connecticut as part of a $1 billion deal.

Both outlets, at 1761 Post Road and 2500 Black Rock Turnpike, and locations in Monroe, Ridgefield, Shelton and Wilton, as listed on HSBC's website, will remain open, according to First Niagara, headquartered in Buffalo, N.Y.

London-based HSBC said its Westport branch at 19 Post Road East will remain an HSBC branch.

HSBC, which will keep two other branches in Stamford and Darien, will close its Norwalk branch along with 12 other operations in New Jersey and New York.

First Niagara will acquire 195 HSBC locations throughout Connecticut, New York and New Jersey. The bank said it may sell 100 of those banks.

On Sunday, First Niagara, which recently acquired New Haven-based NewAlliance Bancorp, and HSBC announced the deal for 195 HSBC branches in New York, Connecticut and New Jersey.

First Niagara said in a U.S. Securities and Exchange Commission filing that it must make an offer of comparable employment to the former HSBC workers at the branches being purchased.

Staff Writer Michael C. Juliano and Bloomberg News contributed to this report.