Former leader of Egyptian Islamist militant group Al-Gama'a al-Islamiyya Omar Abdel-Rahman has died in his US prison after serving more than 20 years for seditious conspiracy to commit murder, his son and daughter have confirmed.

Axar.az reports that, Abdel-Rahman, also known as the Blind Sheik, was serving a life sentence in the United States for his role in masterminding the 1993 World Trade Center bombing.

Reuters news agency reported Abdel-Rahman’s son confirming the death while his daughter Asmaa Abdel-Rahman took to Twitter to announce the news.

The 78-year-old spiritual leader of Al-Gama'a al-Islamiyya, or the Islamic Group, was revered within extremist circles in Egypt during the early 1980s. He was charged on suspicion of involvement in the 1981 assassination of Egyptian leader Anwar Sadat, which he was acquitted of involvement later.