CAIRO (REUTERS) - Egypt's interim administration expressed "deep regret" for those killed in violence in Cairo on Monday, it said in a statement carried on the state news agency.

The statement said the deaths were the result of an attempt by protesters to storm the Republican Guard headquarters where ousted president Mohamed Mursi is believed to be housed. At least 42 people were killed in the clashes, which Islamist demonstrators blamed on the military.

The transitional administration also said it had formed a judicial committee to investigate the events.

The statement called on protesters not to approach any military or "other vital installations".

Violent clashes that led to the deaths in front of Egypt's Republican Guard compound will not derail efforts to form an interim government, presidency spokesman Ahmed Elmoslmany said. "What happened will not stop steps to form a government or a road map," he told Reuters.

Just hours after the shootings, the political arm of the Muslim Brotherhood urged Egyptians to rise up against the military, which is claimed was pushing Egypt into becoming "a new Syria" - an ominous reference to a civil war that has killed more than 93,000p eople since March 2011.

Regardless of the reason, the escalating chaos will further complicate Egypt's relations with Washington and other Western allies, which had supported Mr Mursi as the country's first elected leader and now are reassessing policies toward the military-backed group that forced him out.