Egypt has declared a three-month state of emergency in parts of northern Sinai.
The move comes after two attacks in Sinai killed 33 security personnel on October 24.
Analysts say it was some of the bloodiest antistate violence since Islamist President Muhammad Morsi was overthrown last year.
Officials said 30 people were killed in the first attack in the Al-Kharouba area northwest of Al-Arish, near the Gaza Strip.
Hours later, gunmen opened fire on a checkpoint in Al-Arish, killing three members of the security forces, officials said.
There was no immediate claim of responsibility for either attack.
Similar previous operations have been claimed by Egypt's most active militant group, Ansar Bayt al-Maqdis.