The American talkshow host sent her first "tweet" on Friday and has already amassed more than 350,000 followers.

But users of the microblogging community have blamed her popularity for causing the site to slow down.

Some estimates suggest hundreds of thousands new users may have joined Twitter after Winfrey promoted it on her TV show.

Her profile has also allegedly been the target of a 'worm attack' - which hijacks users' profiles and sends rogue tweets from their accounts.

It has spread messages mentioning Winfrey and actor Ashton Kutcher in what appears to be a deliberate attack on celebrities with profiles.

So far, Winfrey has used her page to chat to celebrity friends including Demi Moore, inform fans what she is eating and talk about her dog.

But users seemed to turn on the famous interviewer, claiming her popularity was overwhelming the site and making it hard to use.

Twitter founder, Evan Williams, who appeared on Oprah the day she launched her feed, was forced to publicly deny the problem was caused by her profile.

He told followers her arrival had a "huge effect" on Friday but his team "kept it under control".

"Site slowness today had nothing to with @Oprah," he insisted.

Users have mocked Winfrey's slow arrival on Twitter by proclaiming they were "here before Oprah".

Other stars who have become popular on Twitter include P Diddy, Stephen Fry and Hugh Jackman.