Egyptian security officials say they used army attack helicopters to fire missiles at suspected Islamic militants in Sinai following simultaneous attacks by armed men on three security checkpoints.
It was the first time Egypt's army has fired missiles in the area since the 1973 war with Israel to recapture the Sinai Peninsula.
The missile strikes came hours after the militant attacks near northern Sinai's main city of Al-Arish, about 50 kilometers from the Gaza-Israel border.
Officials say a military officer, two soldiers, two police and a civilian were injured by the militants early on August 8.
State media quote Egyptian military sources who say 20 militants were killed by the air strikes.
On August 5, militants killed 16 border guards in the area near the Israeli border -- seizing two armored personnel carriers and storming across the border into Israeli territory before they were attacked and killed by Israeli Defense Forces.
Egypt's President Muhammad Morsi vowed to retake "full control" of the Sinai, saying militants would "pay dearly."
U.S. Secretary of State Hillary Clinton on August 7 telephoned Egyptian Prime Minister Hesham Kandil to voice support for Cairo's efforts to strengthen security in Sinai.
Based on reporting by Reuters, AP, AFP and DPA