"The crown prince, (who is also) deputy prime minister and interior minister, arrived in Cleveland from Morocco for medical examinations that had been previously scheduled," the palace said in a brief statement carried by the official SPA news agency. It did not elaborate on what the tests were for. Prince Nayef -- who has served as interior minister for nearly four decades and led the kingdom's post-September 11, 2001 crackdown on Al-Qaeda -- was named crown prince in October last year at the age of 78, following the death of his brother, Prince Sultan. In recent years, he has spent an increasing proportion of his time at his palace in Morocco after handing over day-to-day security activities to his son, Deputy Interior Minister Prince Mohammed bin Nayef. Seen as more conservative than the 87-year-old king, Prince Nayef likes to describe himself as a soldier under the command of the Saudi monarch.