The military said it deployed Apache helicopter gunships in the strikes that killed 20 terrorists in the Sinai village of Tumah near the town of Sheikh Zouaid, the state-run MENA news agency reported.
The pre-dawn raids were apparently in response to deadly attacks on Sunday by militants on a border checkpost, killing 16 soldiers. The air raids marked for the first time in decades that Egyptian military crossed into Sinai, which was declared a de-militiarised zone after the last Arab-Israel war.
Gunships went into action, after army had massed heavy forces close to the Sinai peninsula in anticipation of a major crackdown on the militants.
"Our forces have entered the village of al-Toumah killing 20 terrorists and have destroyed three armoured cars belonging to the terrorists," an army spokesman said, adding "operations are still on going."
The military action followed fresh clashes between armed men and security forces at several security check points overnight in the Sinai region.
Official said armed men believed to be jihadists fired on checkpoints in al-Arish and in the nearby town of Rafah on the border with Gaza, injuring seven people, including two police officers.
Heavy exchange of fire continued late into the night, state-run MENA said. The army closed the roads leading to areas where firing was going on. (MORE)