Who are the terrorists that Islamic militants want freed?

In the latest development surrounding the bloody three-day hostage standoff at a natural gas plant in the Sahara, Algeria's state news service reported that nearly 100 of the 132 foreign workers kidnapped by Islamic militants had been freed. On Friday the militants offered to trade two American hostages for two prominent terror figures jailed in the United States: Omar Abdel Rahman and Aafia Siddiqui.

Abdel Rahman, a blind sheik, is considered the spiritual leader of men convicted in the 1993 World Trade Center bombing. He is serving a life sentence for conspiracies to blow up New York City landmarks, including the United Nations, and assassinate then-Egyptian President Hosni Mubarak.

In September 2003, he was transferred from the federal Supermax prison in Colorado, where the country's most notorious inmates are held, to the U.S. Medical Center for Prisons in Springfield, Mo. Prisons officials said then that Abdel Rahman has suffered from diabetes, which threatened the loss of his limbs.

In a video in September marking the fifth anniversary of the Sept. 11 attacks, al Qaeda's No. 2 man, Ayman al-Zawahri, cited the continuing imprisonment of the sheik. "I call on every Muslim to make use of every opportunity afforded him to take revenge on America for its imprisonment of Sheik Omar Abdel-Rahman," he said.

Most recently Egyptian president Mohammed Morsi had vowed to free the blind sheik in his first public speech in June 2012.

Siddiqui, a Pakistani scientist, was convicted in February 2010 of trying to kill U.S. agents and military officers after she was detained by police in Afghanistan in 2008, and was later sentenced to 86 years in prison. She trained at the Massachusetts Institute of Technology and Brandeis University in the early 1990s. Authorities claim she returned to her native Pakistan in 2003 after marrying an al Qaeda operative related to Khalid Sheikh Mohammed, the admitted mastermind of the Sept. 11, 2001, terrorist attacks.

During Siddiqui's trial, FBI agents and U.S. soldiers testified that when they went to interrogate Siddiqui, she snatched an unattended assault rifle and shot at them while yelling, "Death to Americans!" She was wounded by return fire but recovered and was brought to the United States to face trial.

Though she was not convicted of terrorism, the government has argued that Siddiqui is a cold-blooded radical who deserves a "terrorism enhancement" under federal sentencing guidelines that would guarantee a life term.

Her conviction sparked protests in Pakistan. In September 2010, about 400 activists of the Islamist group Jamaat-e-Islami and its allied youth group, Pasban, gathered outside the Karachi Press Club carrying pictures of Siddiqui and chanting slogans against the U.S. government and justice system.