Eleven Egyptian soldiers were killed and 37 wounded in a car bomb attack near the North Sinai city of El-Arish on Wednesday, a security official said.
The attack was one of the deadliest in the Sinai Peninsula, which is near Israel and the Palestinian-run Gaza Strip, since Al-Qaida-inspired militants began stepping up assaults following the army's ouster of Islamist President Mohammed Morsi in July.
The soldiers were traveling in a convoy on the road to the Rafah border crossing with Gaza. There was no immediate claim of responsibility.
A Sinai-based militant group, Ansar Bayt al-Maqdis, said it assassinated a high-ranking security officer in Cairo on Sunday, according to a statement posted on a militant Islamist website. That group has also said it was behind a failed suicide attack on Egypt's interior minister in September.
In a separate incident on Wednesday, three people were wounded in a bomb attack on a security checkpoint in Cairo, state television reported.
Fears are growing that an Islamist insurgency will take hold beyond Sinai.
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