The messages are mostly coming from disposable accounts, but they also appear on some accounts that appear to be genuine, which indicates that there’s a worm spreading and sending the messages from infected accounts. Furthermore, all of the messages containing the link are sent from the mobile version of Twitter.
The Next Web has traced the origins of the link in the messages, which sends users to a French site (http://artcan-developpement.fr) that has apparently been hacked to forward users to sites containing various malware scripts.
While the majority of the messages currently contain an identical shortened link, have in mind that the link is very likely to change in the future. As always, do not click on any suspicious links, and always keep your computer protected with antivirus and anti-malware software.