Blind Sheik was convicted of World Trade Center truck bombing in 1993

Omar Abdel-Rahman, the so-called Blind Sheik convicted of plotting terror attacks in New York City in the decade before 9/11 and spiritual guide to a generation of Islamic militants, has died in a federal prison. He was 78.

Abdel-Rahman, who had diabetes and coronary artery disease, died Saturday at the Federal Correction Complex in Butner, N. C., said acting Executive Assistant Kenneth McKoy. The inmate spent seven years at the prison medical facility while serving a life sentence.

"We are saddened by your departure, father," the cleric's daughter, Asmaa, tweeted in Arabic.

Abdel-Rahman was a key spiritual leader for militants and became a symbol for radicals during his decades in U.S. prisons, where his captivity inspired plots, protests and calls for violence. The only person charged in the U.S. in the Sept. 11, 2001 attacks, Zacarias Moussaoui, had said he was training for a mission to fly a jet into the White House if the government refused to free Abdel-Rahman.

Blind since infancy from diabetes, Abdel-Rahman was the leader of one of Egypt's most feared militant groups, the Gamaa Islamiya or the "Islamic Group," which at its height led a campaign of violence aimed at toppling that country's onetime president, Hosni Mubarak.

Abdel-Rahman fled Egypt to the U.S. in 1990 and began teaching in a New Jersey mosque. A circle of his followers were convicted in the Feb. 26, 1993, truck bombing of New York's World Trade Center that killed six people — eight years before al-Qaida's suicide plane hijackers brought the towers down.

Later in 1993, Abdel-Rahman was arrested by authorities who accused him and others of conspiring to bomb the United Nations and other New York landmarks, including the George Washington Bridge and the Lincoln and Holland tunnels. Those attacks were never carried out.

Since his imprisonment, Abdel-Rahman's influence had been seen as more symbolic than that of a practical leader. His Gamaa Islamiya, which led a wave of violence in the 1990s against Western tourists, Egyptian police and Coptic Christians, was eventually crushed, and its leaders — jailed in Egypt — declared a truce.

Abdel-Rahman's activities pre-dated Osama bin Laden's formation of al-Qaida in the late 1990s. But he was an influential figure in the generation of Islamic extremists that emerged from Egypt in recent decades.

He shared an ideology with another prominent group at the time, Islamic Jihad, that rejected the governments of Egypt and other Arab countries as infidels that must be brought down by force.

After the death of Egyptian President Gamal Abdel-Nasser in 1970, Abdel-Rahman told followers not to pray for the soul of the leader of secular Arab nationalism because he was an infidel, which got him eight months in prison.

After the 1981 assassination of President Anwar Sadat by Islamic militants, Abdel-Rahman was jailed and accused of sanctioning the killing. He was later acquitted. Even though Abdel-Rahman was on a list of suspected terrorists and banned from the U.S., he managed to enter the country in 1990 because of a bureaucratic blunder. He was given permanent residence status under the name Omar Ahmed Ali.