The sons of former president Hosni Mubarak were freed from prison on bail in the early hours of Friday pending retrial in a corruption case, a prison source told Al-Ahram Arabic news website.

Alaa and Gamal Mubarak left jail at dawn after a court ordered their release a day earlier because they had already served the maximum period of 18 months in pre-trial detention, Al-Ahram reported.

Along with their father, they are facing a retrial on corruption charges, ordered by an appeals court earlier this month.

The decision overturned a lower court conviction that saw the pair given four-year jail sentences, and their father jailed for three years.

They were charged with embezzling public funds earmarked for the renovation of presidential palaces and using the money to spruce up private properties.

Their release came two days ahead of the anniversary of the popular revolt that ended three decades of rule by long-time autocrat Mubarak.

A Cairo court had already dropped other graft charges against the two sons in November, as well as clearing Mubarak of charges of complicity in the killing of protesters in the 2011 uprising.

The court rulings have provoked anxiety that figures associated with the Mubarak regime may return to public life.