The error message being displayed on Bank of America&39's home page.

Bank of America's online-banking service is down for U.S. customers.

When users across the U.S. try to access their online banking, the Bank of America home page displays a message saying "online banking is temporarily unavailable." It provides no indication of when the service should be back up and running.

Bank of America has stopped short of calling the issue an outright "outage." Company spokeswoman Tara Burke told CNET in a phone conversation today that an update to BofA's Web site over the weekend is causing the "intermittent service disruptions." She also noted that the issue "is not impacting customer information or compromising customer security."

According to a Bank of America technical-support person who also spoke with CNET by phone today, the problem first occurred yesterday afternoon. The company was able to restore service this morning, only to see it go down "nationwide" a few hours later.

As one might expect, upset customers have taken to Twitter to express displeasure. A search of "Bank of America outage" on the social network reveals dozens of tweets referencing the issue hitting the site every minute. One of the more comedic comments came from a user coming to the conclusion that the outage "must mean Bank of America doesn't want my mortgage payment."

In her conversation with CNET, Burke wouldn't say how many customers have been affected by the issue. She also didn't provide any more details about the problem. She would say only that the company is working on a fix.

"We're looking to restore capability as quickly as possible," she said.

We will update this story as we learn more.

CNET's Elinor Mills contributed to this report