The Sinai mosque attackers were carrying the flags of Islamic State (IS, formerly ISIS/ISIL) group, Ahram news agency reports citing the public prosecutor’s office. There were around 25-30 militants, the statement said, adding that the death toll has risen to 305.

The militants arrived at the Bir al-Abd mosque in five all-terrain vehicles, took up positions at the mosque’s door and 12 windows and started firing on worshippers inside, Egypt’s chief prosecutor Nabil Sadeq said in a statement Saturday. They are also said to have set fire to seven cars parked outside the mosque.

People ran for their lives after the gunmen detonated a bomb at Al-Rawdah mosque at the end of Friday prayers. They then opened fire on those fleeing and ambulances that arrived at the scene.

According to the Egyptian Al-Masry Al-Youm newspaper, the prosecutor has been hearing witnesses who confirmed that some of the attackers were masked, while all were dressed in military-style clothes. One of the perpetrators was reportedly carrying a black flag, saying “I bear witness that there is no God but Allah, that Muhammad is the Messenger of Allah.”

READ MORE: 'They shot at ambulances': 235 dead, scores injured in bomb & gun attack at Sinai mosque (GRAPHIC)

So far, no group has claimed responsibility for what is believed to be the worst attack in Egypt’s recent history. The country’s president Abdel Fattah al-Sisi vowed“the military and the police will take revenge,” saying the attack has only prompted Cairo to step up its efforts in targeting terrorism.

Following the Friday slaughter, the military conducted air strikes and raids overnight in North Sinai “to comb terrorist hideouts and find and eliminate the rest of extremists,” Ahram newspaper cited the army spokesman Tamer El-Refaie as saying. A number of terrorists have been killed in the operation, led by the air force and law enforcement, he added.

To honor the victims, the Egyptian leader announced a three-day period of mourning and ordered the building of a memorial. He also directed that the relatives of those killed, as well as the injured, be paid a compensation.