Clashes erupted across much of Egypt between security forces and supporters of the ousted president on Sunday, leaving 28 killed, as rival crowds of supporters of the military and backers of the Islamist Mohammed Morsi poured into streets around the country to mark a major holiday.

The clashes took place on the day 40 years ago when Egyptian forces crossed the Suez Canal at the start of the nation’s last war with Israel. The day has since been declared a national holiday. The military-backed government had wanted the anniversary celebration to be a tribute to the armed forces, whose chief ousted the Islamist Mohammed Morsi in a popularly supported coup on July 3.