Cairo: Egypt’s top appeals court Wednesday turned down a legal challenge from prosecutors against exonerating dozens of former senior officials and lawmakers of involvement in a deadly attack against opponents of the toppled president Hosni Mubarak more than two years ago.

The verdict by the Court of Cassation puts to a fresh test the credibility of the Islamist President Mohammad Mursi who has repeatedly vowed to bring to justice suspects in protester deaths during the 2011 revolt that ousted Mubarak.

In October last year, the Cairo Criminal Court acquitted all 24 defendants in what is locally known as the “Camel battle” case, citing lack of evidence.

Scores of machete-wielding thugs, riding on the backs of camels and horses, attacked protesters in Tahrir Square in central Cairo on two consecutive days in February 2011 at the height of the uprising against the Mubarak regime.

The defendants included Safwat Al Sherif, the secretary-general of Mubarak’s National Democratic Party, Fathi Surour; a former speaker of parliament; Aisha Abdul Hadi a former minister of manpower, and several ex- MPs from the formerly governing party.

Around 11 people were killed and 2,000 injured in the attack, which was carried out on February 2 and 3, a few days before Mubarak was forced to step down.

Now that the Court of Cassation has upheld the acquittals, prosecutors will have to come up with new evidence before a new trial could open, according to legal experts.

Early this year, Mursi ordered the formation of the “Revolution Prosecution”, a committee of prosecutors tasked with finding evidence and investigating cases related to killing and injuring protesters during the anti-Mubarak revolt.

Around 846 people were killed and 6,000 wounded in the 18-day revolt, according to an independent fact-finding commission.

Meanwhile, the Illicit Gains Authority Wednesday extended by a further 15 days the detention of Mubarak for alleged graft, reported state-run media.

A criminal court is due Saturday to start the trial of Mubarak, 85, and his interior minister Habib Al Adly on charges of complicity in the protester killings.

Both had been sentenced to life in prison before their appeals were granted and a new trial ordered for them. Mubarak and his two sons are also facing charges of corruption.