GoDaddy said it is working on resolving a problem that has caused many of the sites it hosts to go offline.

"Status Alert: Hey, all. We're aware of the trouble people are having with our site. We're working on it," the company tweeted Monday morning.

Some GoDaddy sites began experiencing problems after 10:00 a.m. PDT, and a quick search of "GoDaddy" on Twitter indicated that the issues are likely extensive. Many users are sending tweets saying all of their websites are down.

"Awesome. My @GoDaddy hosted site is down....as is their site. #NoDaddy," tweeted @MinorLeagueBlog, the Twitter account for TopProspectAlert.com, a site that was affected.

Some on Twitter say every site hosted by GoDaddy is down, but the company has not confirmed that. Its own site was running slowly after sites began going offline, although it appeared to be working fine later.

The hacker group Anonymous took responsibility for the problems, with one user sending the following tweet around the time sites started going offline: "Hello everyone who wanna me to put 99% of the global Internet in #tangodown?"

Not long after, another Anonymous-associated Twitter account tweeted "#TangoDown," which members of the group tend to do when they claim to successfully attack a target.

The group may have hit GoDaddy with a denial-of-service attack, which bombards a site with more traffic than it can handle and crashes it.