Former chief of the Egyptian intelligence service Omar Sulaiman on Tuesday testified in the trial of president Hosni Mubarak, indicted for ordering the killing of protesters and corruption.

Sulaiman, who was picked by Mubarak to be vice president at the peak of a popular revolt in late January, was cross-examined by the court and defence lawyers at a session held behind closed doors, state Egyptian television reported.

The court ordered a media gag on leaked details from Sulaiman's testimony and those to be given later this month by chief of Egypt's ruling military council Husseain Tantawi and incumbent army chief of staff Samy Anan -  for "national security considerations".

Their testimonies are seen crucial for either clearing or convicting 83-year-old ailing Mubarak.

Sulaiman served as Egypt's spymaster for long years and was seen as a potential successor to Mubarak, who was forced to step down in February.

In pre-trial depositions, Sulaiman echoed previous testimony of security officials, saying he was unaware of orders by Mubarak to shoot at protesters earlier this year.

"Policemen cannot open fire to disperse demonstrators without orders from the interior minister," Sulaiman told investigators.

Standing as co-defendants in same trial are Mubarak's two sons, former interior minister Habib Al Adli, and six security aides.

At least 846 people were killed and more than 6,000 injured during the riots that ultimately led to Mubarak's ouster.