Square Inc, the payments company founded by Twitter Inc. Chief Executive Jack Dorsey, has launched a new service that enables customers of its small-business clients to pay for purchases in installments, the company said on Thursday. Through Square Installments, the San Francisco-based company will be extending credit to the customers of merchants that use its technology to accept payments online and in-store for purchases ranging between $250 and $10,000. Borrowers will be able to repay in fixed monthly payments over a period of three, six or 12 months. Interest rates will range between 0 and 24 percent. Merchants will receive the payment upfront and Square will be holding the loans on its balance sheet.