Apple CEO Steve Jobs, the charismatic frontman for the company that transformed the smart phone industry and launched a new era in tablet computers, is taking another stint of medical leave. The company disclosed the news early on a U.S. holiday when U.S. markets were closed, and didn't specify why or for how long its visionary leader would be absent.

Apple announces that Executive Steve Jobs will take a medical leave for the second time in as many years.

Apple shares tumbled more than 8 percent in Frankfurt on the news.

Oliver Roth, Trader of Close Brothers Seydler Bank AG said "Steve Jobs is the heart and the brain of Apple and as long as nobody knows how long he will be away, speculation in Apple will go on and that will put pressure on the stock price."

The news, which was disclosed early on a U.S. holiday when markets were closed, came nearly two years to the date after Jobs first took a six-month break to undergo a liver transplant.

Apple's destiny has been closely tied to the charismatic Jobs, who revived the computer maker's fortunes in 1996 after a 12-year absence from the company he co-founded.