Human Rights Advisory Council spokesman al-Tayeb Haroun Abbas did not name the remaining eight detainees apart from Turabi, head of the Popular Congress party who was arrested in February 2001.
The nine are the last political detainees in Sudanese jails after the recent release of 32 others, he told a press conference.
The claim could not be independently confirmed.
Although Human Rights Advisory Council is a body headed by Justice Minister Ali Mohamed, it is not clear whether the call to free Turabi by the body signals the government's intention to release him soon.
In a report issued last month by Amnesty International on Sudan, they said that "incommunicado detention of political opponents, students and ordinary citizens as well as torture by the security forces remain common.”
"Above all, the lack of judicial accountability of the security forces for any action they take, including acts of torture, is maintained in laws which are inconsistent with international human rights principles," Amnesty added.
Around two million have been killed in Sudan since the civil war began in 1983.