Wells Fargo (WFC) on Thursday endured the second cyberattack the company has acknowledged in as many weeks.

The digital assault on the nation’s fourth-biggest bank jammed online and mobile banking and left some customers unable to log in to their accounts.

"We're experiencing a denial of service attack, which is a deliberate attempt to disrupt website access by flooding a site with traffic, similar to a cyber traffic jam," Wells Fargo wrote on the company’s Facebook page. "If you're having difficulty accessing the site or mobile banking, try logging on again as the disruption is usually intermittent."

Wells Fargo also took to Twitter to say the onslaught was "causing online & mobile issues."

The website Sitedown.co on Thursday afternoon logged roughly 178 reports of people being unable to log in to their accounts at Wells Fargo within the preceding 24 hours compared with 185 such reports in the past seven days.

The attack comes nine days after Well Fargo suffered a similar attack. American Express (AXP) and BB&T (BBT) have weathered denial of service attacks in the past week as well. KeyCorp (KEY) also said its websites had experienced intermittent slowdowns.

Electronic assaults also bogged down online banking in March at TD Bank and JPMorgan Chase (JPM).

The al-Qassam Cyber Fighters, a group of hacktivists who have claimed responsibility for a string of denial of service attacks on some of world’s largest financial institutions, in an email Tuesday threatened attacks on six financial institutions. Though the missive omitted mention of Wells Fargo, the group has previously targeted the San Francisco-based bank.