Some Twitter users had to do without early Tuesday after sporadic outages knocked the social media site offline in the U.S. and Europe.

Reports of malfunctions began to appear in the U.S. as well, but it was unclear how widespread the outages were. By mid-morning on the East Coast, desktop and mobile versions of Twitter appeared to be working, though the company wouldn't say if they were back to normal.

A company spokeswoman also wouldn't reveal any details as to the possible cause of the outage, declining to comment beyond Twitter's tweeted statement.

Twitter Inc. which has 320 million active users, tweeted that it is aware of the issue and is trying to fix it. Its most recent notice was sent around 4 a.m. Eastern.

Users said the service was not accessible on desktop computers. Twitter's blog posts, corporate info and most other pages on the Twitter.com website were also inaccessible, displaying the blue error screen.

There were complaints of users receiving a "server error" just before 8 a.m. Eastern.

Twitter's mobile app was partially functioning for some users but its timeline updated new tweets sporadically. Its search function appeared disabled as some hashtags or keyword searches returned no results. Users' profile pages appeared to be accessible from the mobile app.

Third party services, such as the TweetDeck service, also returned a blank page.

Twitter has suffered several service disruptions so far this year. On Monday, some users could not access Twitter on mobile and web for about 10 minutes. The service was disrupted on Friday for about 20 minutes.

The outages come at a time when Twitter and its executives are trying to convince Wall Street that they can deliver bigger revenue and profits. Meanwhile, the company's stock continues to languish at an all-time low. Twitter share have lost 66 percent of their value since peaking at $52.87 in April.

In morning trading Tuesday, Twitter shares fell 35 cents to $17.59.