Reuters was not able to determine when the outage began.
Glitches continue to trouble Citigroup, as the financial-services company said Monday that some credit card customers were unable to access their accounts via the Web.
Citigroup is the largest company in the world with $2.2 trillion in assets.
The company issued a statement to the news service: “This is a temporary interruption and we anticipate that the site will be back up in the next few hours.”
Reuters reported that an undisclosed number of Citicard owners could not access the card’s online account service. This is the second such malfunction of one of Citigroup’s sites in a week. Citibank saw intermittent outages to its Web site last Tuesday.