Britney Spears is among a handful of celebrities targeted by online pranksters who hacked high-profile accounts on networking site Twitter on Monday.

Twitter is a social networking service that allows users to keep in touch with people through the exchange of quick, frequent answers to the question “What are you doing today?”

Hackers wrote: “Hi Y’all! Brit Brit here, just wanted to update you all on the size of my vagina. It’s about four feet wide with razor sharp teeth.”

President-Elect Barack Obama, political commentator Bill O’Reilly, and newscaster Rick Sanchez also saw their Twitter accounts compromised.

The Obama hacker sent out false “tweets” offering $500 worth of free gas in exchange for filling out a questionnaire.

More than 155,000 users follow Obama’s updates and received the following questionnaire: “What is your opinion on Barack Obama? Take the survey and possibly win $500 in free gas.”

Site officials removed the offensive messages, and insists they are working to make Twitter more secure.

“A number of high-profile Twitter accounts were compromised this morning, and fake/spam updates were sent on their behalf. We have identified the cause and blocked it. We are working to restore compromised accounts,” site administrators said in a statement.