Omar Ahmad Rahman, the so-called “Blind Sheik” convicted of plotting terror attacks in the United States in the 1990s, died Saturday in a federal prison where he was serving a life sentence. He was 78.

Rahman died at 5:40 a.m. after suffering from diabetes and coronary artery disease, said Kenneth McKoy at the Federal Correction Complex in Butner, North Carolina. He had been at the complex for seven years.

Rahman had a suspected link to the bombing of the World Trade Center in 1993 but was never convicted, CBS News senior investigative producer Pat Milton reports.

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Rahman’s daughter, Asmaa, announced the death in a series of Arabic-language tweets: “We are saddened by your departure, father,” she wrote.

“Blind Sheik” Omar Ahmad Rahman sits and prays inside an iron cage at the opening of court session in Cairo Aug. 6, 1989. AFP/Getty Images

Rahman was a key spiritual leader for a generation of Islamic militants and became a symbol for radicals during two decades in American prisons.

Blind since infancy from diabetes, Rahman was the leader of one of Egypt’s most feared militant groups, the Gamaa Islamiya, which led a campaign of violence aimed at bringing down ex-President Hosni Mubarak.

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 Qaeda’s suicide plane hijackers brought the towers down.

Later in 1993, Rahman was arrested by authorities who accused him and others of conspiring to wage a string of bombings against the United Nations and other New York landmarks, including the George Washington Bridge and the Lincoln and Holland tunnels.

But since his imprisonment, Rahman’s influence had been seen more as symbolic than that of a practical leader. His Gamaa Islamiya, which led a wave of violence in the 1990s, was crushed a decade ago, and its leaders, jailed in Egypt, declared a truce.

Rahman’s activities pre-dated Osama bin Laden’s formation of al Qaeda in the late 1990s. But he was an influential figure in the generation of Islamic extremists that emerged from Egypt over the past two decades.

While Rahman was the spiritual leader of Gamaa Islamiya, his longtime associate from Egyptian militant circles, Ayman al-Zawahri, was a leader of the Islamic Jihad militant group, whose experienced fighters he later allied with bin Laden’s riches to form al Qaeda. Al-Zawahri is now leader of al Qaeda.

The two groups shared an ideology rejecting the governments of Egypt and other Arab countries as infidels that must be brought down by force. Between 1990 and 1996, they carried out a wave of attacks on Western tourists, Egyptian police and Coptic Christians until a heavy-handed government crackdown largely shattered them.