The militants who carried out an attack during Friday prayers at a mosque in Egypt's Sinai peninsula were carrying ISIS flags, the country's chief prosecutor, Nabil Sadeq, said Saturday.
Sadeq also said that the death toll has risen to 305 worshipers, including 27 children -- a dramatic increase from the previously announced 235 fatalities. Another 128 were injured, he added.
Friday's attack was carried out by 25-30 militants who arrived at the mosque in five all-terrain vehicles, according to Egypt's chief prosecutor. They also torched seven cars belonging to the worshipers that were parked outside, Sadeq added.
Worshipers told Sadeq's office that some of the attackers wore masks, but all wore military-like uniforms.
Emblazoned on the ISIS flags was the phrase, "There is no god but God. Muhammad is the messenger of God," according to survivors of the attack.
Later Saturday, the Egyptian government placed the blame on ISIS, citing eyewitnesses who saw the flag-wielding attackers. Since the attack, the Egyptian military has carried out multiple airstrikes on bases it says are used by ISIS militants in the restive North Sinai region.
An eyewitness described the perpetrators as having stationed themselves at the mosque's three exits and deliberately attacking people who tried to escape the building, as well as passing vehicles, after first shooting some who were "kneeling in prayer."
"The sight was horrific," the witness, Ibrahim Shetewy, told ABC News in Arabic, adding, "We carried whomever we found alive and took them in pickups and private cars until more ambulances could come and help."
Shetewy described the mosque in question as one frequented by travelers on their way in and out of the area. He said the building is "huge" and was lined with bodies and a large quantity of shell casings following the attack.
"There was a woman waiting outside for her husband and young child to finish praying; she came inside and found them dead next to each other," Shetewy said.
He added that people are lined up at a local hospital to donate blood.
An additional local resident present at the Beir El-Abd hospital, which received victims in the aftermath, described the wounded arriving at a rate beyond the capacity of the hospital, which is between 25 to 30 miles away from the targeted mosque. The resident added that urgent cases are being sent to another hospital in Ismailia, almost 75 miles away.
The Egyptian Armed Forces posted to Facebook on Saturday a video of its aircraft targeting "terrorist spots" in northern Sinai.
"The law enforcement forces continued to pursue the elements responsible for the brutal terrorist incident targeting the worshipers in Northern Sinai, and based on confirmed intelligence ... the Air Force has over the past hours eliminated a number of spots," read the post. "The law enforcement forces, in cooperation with the air force, continue to carry out their operations and have established an intensive perimeter to scour the area around the event in search of the remaining terrorist elements."
Egyptian President Abdel-Fattah el-Sissi vowed that the attack "will not go unpunished." On Saturday, he ordered that a mausoleum be built in memory of the victims and cancelled a visit to the Gulf Sultanate of Oman that was scheduled for next week.
U.S. President Donald Trump commented on the attack via Twitter on Friday morning, writing that it was a "horrible and cowardly terrorist attack on innocent and defenseless worshipers."
"The world cannot tolerate terrorism, we must defeat them militarily and discredit the extremist ideology that forms the basis of their existence!" he continued.
Trump announced Friday afternoon that he planned to call the Egyptian president to discuss the attack.
Two photographs taken after the attack each show more than a dozen bloodstained bodies lined up on the ground of a building as those who appear uninjured tend to them.
The Eiffel Tower in Paris went dark Friday night to pay tribute to the victims of the attack.
ABC News' Morgan Winsor contributed to this report.