QUITO, Ecuador—Customers of Ecuador’s largest bank continued to experience service disruptions on Friday following a cyberattack on the institution several days earlier. Long lines formed outside Pichincha bank branches and thousands of customers took their complaints to social media. People reported being unable to access services offered by the bank’s online and mobile app. ATMs worked somewhat regularly and branches remained open. The bank in a statement Monday acknowledged that it had “identified a cybersecurity incident in our systems that has partially disabled our services.” Its largest shareholder, Fidel Egas, wrote on Twitter that “We are doing the impossible. They want to blame us for something in which we are the victims.” The government’s Superintendency of Banks sent a delegation to the bank’s headquarters to monitor the problems and solutions. That bank has about 1.5 million clients and some $1.5 billion in its portfolio.