Sudanese authorities have begun to recover billions of dollars of real estate illegally amassed by deposed dictator Omar al-Bashir's regime, but other assets will be difficult to seize, experts say.

"Initial estimates indicate that the real estate and properties owned by the former regime... range (in value) from $3.5 to $4 billion," said Salah Manaa, a spokesman for a committee tasked with fighting corruption and dismantling the old regime.

"This is only the tip of the iceberg", in terms of the total assets illicitly accumulated and hidden under Bashir's rule, Manaa told AFP.

Bashir ruled Sudan with an iron fist for 30 years, but was overthrown in April last year by the military during mass protests against him.

He has already been sentenced to two years detention in one corruption case -- involving illegal possession of foreign currency -- and is being held in Khartoum's Kober prison, on a range of other charges.

The new anti-graft committee began work in December and is answerable to a power-sharing government of civilians and generals that was established in August.