Saudi Crown Prince Nayef (Naif) bin Abdulaziz Al Saud, heir-apparent to King Abdullah and a staunch enemy of al-Qaeda as head of Saudi Arabia's Interior Ministry, died today at 78, according to the International Islamic News Agency. Nayef's death reopens the question of who will succeed King Abdullah.

Prince Nayef's death comes as a bit of a surprise as he made a televised appearance in Geneva, Switzerland, just three days ago, although he had left the country several times in recent months for medical tests, according to Al Jazeera. Nayef's brother Prince Ahmed bin Abdulaziz said less than two weeks ago that the heir-apparent was in good health.

Nayef was appointed crown prince and deputy premier on October 27 last year following the death of his brother Prince Sultan bin Abdul Aziz on October 22, 2011. Nayef's death, though, has reopened the question of who will succeed to Saudi Arabia's throne once octogenarian King Abdullah passes away. Saudi Arabia is the world's largest oil producer and a key player in the United States' global anti-terrorism campaign.

With Crown Prince Nayef's passing, Saudi Arabia's leader, King Abdullah, has now outlived two of his designated successors despite his own ailments, according to Al Jazeera. Whoever the new heir-apparent winds up being, he will have to come from among King Abdullah's brothers and half-brothers, children of Saudi Arabia's founder Abdul-Aziz. The best guess at the moment is that the next heir to the throne will be Prince Salman, Saudi Arabia's current defense minister and a former governor of the capital city of Riyadh.

King Abdullah does not have sole say on who will inhering the throne. The next crown prince will be chosen by the Allegiance Council, which is made up of Abdul-Aziz' sons and grandchildren, according to Al Jazeera.

The editor-in-chief of the Saudi Gazette told the Arab news service that there was no cause for alarm following the death of Nayef. Succession in the house of Saud has traditionally been orderly and without drama.

The Saudi Arabian Tadawul All Share Index (SASEIDX) plunged 2.7 percent to 6,565.82 according to Bloomberg News, and it reached its lowest level since Jan. 31. However, Nayef's death is not expected to bring major tremors to Saudi markets, analysts say.

Should Salman be selected as the next crown prince, he would not bring youth to the Saudi throne. Salman himself is 76, according to Al Jazeera.