MasterCard has blamed the outage, which its website suffered on Tuesday, on an Internet Service Provider.
However, the company has not dismissed claims by hackers that they were behind the disruption.
MasterCard had then issued a statement saying, "It is important to note that no cardholder data has been impacted and that cardholders can continue to use their cards securely."
"We are continuing to monitor the situation closely," the credit-card company said.
On Tuesday, soon after it was noticed that the MasterCard website was down, a Twitter user, under the name ibomhacktivist, promoted "MasterCard.com DOWN!!!". The user also said that the hack attack was because the credit card company had messed with WikiLeaks and Anonymous in the past.
"MasterCard’s corporate, public-facing Website experienced intermittent service disruption, due to a telecommunications/Internet Service Provider outage that impacted multiple users," a MasterCard spokesman said.
Meanwhile, the hacker group Anonymous has attacked a US tourism website in Orlando, Florida, to protest against the arrests of people distributing food to the city’s homeless.
