Sudan's criminal prosecutors summoned ousted president Omar Al-Bashir to question him over the 1989 military coup, which brought him to power.
Last May, the prosecution had charged Bashir and his aides with undermining the constitutional system in the context of the 1989 coup.
In June, prosecutors heard the testimony of the head of the opposition National Ummah Party Sadiq Al-Mahdi, and in November they heard Ibrahim Al-Sanoussi, the Secretary-General of the Popular Arab and Islamic Congress.
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Prosecutors also asked the prison service to question Bashir and a number of his aides over their role in the coup of 30 June 1989.
Mahdi was serving as prime minister of the country before Bashir launched a coup and ousted his government. After the coup, Bashir became the country's president.
Last April, Bashir, who served as the country's president for 30 years, was detained in Koper Prison in Khartoum after he was ousted in a popular uprising against his rule.