Rupert Murdoch offered presumptive GOP nominee Mitt Romney some unsolicited advice on Twitter Sunday: Lose your friends and hire professionals.

"Met Romney last week," the 81-year-old chairman of News Corp. wrote. "Tough O Chicago pros will be hard to beat unless he drops old friends from team and hires some real pros. Doubtful."

The message wasn't the first time Murdoch has used Twitter to offer sharp criticism of Romney. Last week he slammed the former Massachusetts governor and two-time presidential candidate for his immigration position.

"When is Romney going to look like a challenger? Seems to play everything safe, make no news except burn off Hispanics," Murdoch wrote.

Murdoch's conglomerate, News Corp., owns media properties across the globe, including the Wall Street Journal and Fox News Channel in the United States. In Britain, his newspaper empire includes The Sun and the Sunday Times. In 2011 and 2012, Murdoch has been embroiled in a scandal involving alleged phone hacking at some of his newspaper holdings.

While some of Murdoch's media titles -- including Fox News and the New York Post -- carry known conservative leanings editorially, the man himself has been known to support candidates of both parties. In 2006, he was reported to have held a fund-raiser for then-Sen. Hillary Clinton, a Democrat, and in 2008, he called then-candidate Barack Obama a "rock star" and praised his education plan. In 2010, News Corp. gave a $1 million donation to the Republican Governors Association.

Murdoch, a native of Australia and a naturalized American citizen, is a regular tweeter, sending several messages per week and responding to his followers when they write to him with questions.

Aside from his candid thoughts on Romney, Murdoch also weighed in on this week's bombshell celebrity headline.

"Scientology back in news. Very weird cult, but big, big money involved with Tom Cruise either number two or three in hierarchy," Murdoch wrote.