Ibrahim al-Sadeq al-Qaidy (search), in his 30s, had surrendered to Saudi diplomats in Damascus, Syria, and was flown into the kingdom on Saturday.
Al-Qaidy had fought alongside Islamic extremists in Afghanistan and Bosnia, but more recently had been in hiding in Syria, the official said, on condition of anonymity.
It was not clear what charges he faced.
After a series of homicide bombings, gunbattles and kidnappings blamed on Al Qaeda (search) members or sympathizers, King Fahd issued an amnesty offer, saying his government would not seek the death penalty against militants who turned themselves in. At the same time, security forces have stepped up efforts to capture those who don't give up.
Al-Qaidy was the fourth to respond. The most prominent of the four, Khaled bin Ouda bin Mohammed al-Harby, returned home Tuesday after surrendering in Iran. Al-Harby was a confidant of Al Qaeda chief Usama bin Laden, a Saudi-born dissident who portrays the United States as the enemy of Islam and the Saudi royal family as too close to America.
Under King Fahd's amnesty offer, militants involved in attacks who turn themselves in will still face trial but the state will not seek their execution if convicted. Those who have surrendered have reported being treated well and at least one has been left in his family's custody until summoned for investigation.
On Tuesday, Interior Minister Prince Nayef said there would be no extension of the one-month amnesty, which expires Friday.