"The protection of the nation is the responsibility of everyone. We will confront any threat to its security with force and firmness within the remit of the law," Mursi said, offering condolences to families of victims in the canal zone cities.
Most deaths were in Port Said, where 40 people were killed in just two days. Riots were sparked on Saturday when a court sentenced to death several people from the city in a case of deadly soccer violence last year.
The violence in Egyptian cities has now extended to a fifth day. Police again fired volleys of teargas at dozens of youths hurling stones early on Sunday near Cairo's Tahrir Square, where opponents have camped for weeks to protest.
The president called for a national dialogue on Monday at 6 p.m. (1600 GMT) to discuss the crisis.
The main opposition National Salvation Front coalition said it would meet on Monday to discuss the offer.