Ten Egyptian soldiers were killed and 35 wounded in a car bomb near the North Sinai city of El-Arish, a security official has said.
The soldiers were travelling in a convoy ahead of the attack.
The attack is one of the deadliest in the Sinai Peninsula since al Qaeda-inspired militants began stepping up assaults following the army's ousting of Islamist President Mohamed Morsi in July.
More top news
The First Lady gave an enthusiastic backing for the Democratic presidential frontrunner in a speech at the Democratic National Convention.
Vitaly Stepanov, who helped uncover the Russian doping scandal, says the IOC is less concerned about ridding world sport of drug cheats.
Colombian drug lord Daniel Barrera Barrera was fined $10m for manufacturing hundreds of tonnes of cocaine that he trafficked globally.