Egyptian officials on Saturday said gunmen in a brutal attack on a North Sinai mosque a day earlier were carrying an Islamic State flag. “They numbered between 25 and 30, carrying the Daesh flag and took up positions in front of the mosque door and its 12 windows with automatic rifles,” Egypt’s public prosecutor’s office said in a statement, using the Arabic term for Islamic State. Gunmen set off a bomb before blocking the mosque’s windows and doors and firing inside as people tried to flee, authorities said. The news came as the death toll climbed to 305 people, including 27 children. Another 128 people were wounded. Egypt’s military said it carried out overnight airstrikes and raids on militants believed to be involved in the attack, the deadliest so far in the country’s modern history.