Islamic State flags were flown by mosque bombers in Egypt, according to the prosecutor.
According to the Ahram news agency, citing the Prosecutor, these are 25-30 bombers who were carrying ISIS flags during the attack.
Egyptian President Abdul Fattah al-Sisi has vowed to respond with "utmost force" after a bloodbath at a North Sinai mosque during Friday prayers that killed more than 300 people, bringing the total to 305.
The Egyptian army says it has carried out airstrikes on "terrorist" targets in response.
No group has yet officially claimed responsibility for the attack, the deadliest in recent years.
On Saturday, the President of the Republic Nikos Anastasiadis had, who.
After the bombs exploded, dozens of gunmen waiting outside the mosque opened fire on those trying to escape.
The assailants reportedly set fire to parked vehicles to block access to the building and shot at ambulances trying to help the victims.
Thirty children are among the dead and at least 100 people have been injured.
Locals say the al-Rawda mosque is used by the local Sawarka tribe, which is known to co-operate with security services against militants.
Egypt's response
An army spokesman said "terrorist spots", where weapons and ammunition were stored, had been bombed by jets on Friday in response.
The official also said that various vehicles used for the attack had been located and destroyed.
Three days of mourning have been declared in the country.