"Today we discovered about 750 Twitter accounts were broken into and had a link to a webcam site posted on the accounts," the company said on its blog on Friday. "It appears other sites and services have been affected by a similar attack.
"We reset the passwords of the compromised accounts and removed the spammy updates. Our safety team is currently investigating the attack."
The message said: "Hey! 23/Female. Come chat with me on my webcam thingy here: www.ChatWebcamFree.com."
The site was not accessible at post time.
Facebook users last month were hit with a similar attack promoting the same adult chat site, according to a security analyst.