Updated

The revolutions that swept the Middle East and North Africa also emptied prisons of militants, a problem now emerging as a potential new terrorist threat.

Fighters linked to one freed militant, Muhammad Jamal Abu Ahmad, took part in the Sept. 11 attack on U.S. diplomatic outposts in Libya that killed four Americans, U.S. officials believe based on initial reports. Intelligence reports suggest that some of the attackers trained at camps he established in the Libyan Desert, a former U.S. official said.

Western officials say Mr. Ahmad has petitioned the chief of Al Qaeda, to whom he has long ties, for permission to launch an Al Qaeda affiliate and has secured financing from Al Qaeda's Yemeni wing.

U.S. spy agencies have been tracking Mr. Ahmad's activities for several months. The Benghazi attacks gave a major boost to his prominence in their eyes. Mr. Ahmad, although believed to be one of the most potent of the new militant operatives emerging from the chaos of the Arab Spring, isn't the only one, according to Western officials.

They say others are also trying to exploit weaknesses in newly established governments and develop a capacity for strikes that could go well beyond recent violent protests in Libya, Egypt and elsewhere.

More On This...

    The U.S. and its allies hoped the revolutions of last year would lead to a more stable, more democratic and more U.S.-friendly Middle East. That may still come to pass. But in the near term, they face a growing number of security threats-not only the violence around the release of an anti-Islamic video but also terrorist attacks in Egypt's Sinai Peninsula and gains made in Yemen by Al Qaeda's affiliate there.

    Click for more from The Wall Street Journal.