Attacks in the region have increased following the July 3 military coup that toppled President Mohammed Morsi, an Islamist, prompting the military offensive.
Early Saturday, resident say they saw winding columns of trucks and armored vehicles pour into the area. Some said they hadn't seen soldiers on foot in their villages in decades. Communications were jammed for hours, as authorities seized control of two telephone exchanges.
Military helicopters hovered overhead in a dozen villages concentrated near two border towns of Rafah and Sheikh Zuweyid, security officials said. Airstrikes targeted shacks believed to be gathering points of militants, they said. Soldiers later stormed homes searching for suspected fighters.
"Successive strikes are aimed at causing paralysis of the militant groups and cutting communications between each other," a security official said. "The offensive is carried out within a timeframe where there will be periods of calm for intelligence before resuming once again."
"We aim for cleansing the whole region of militants and prevent them from coming back," he added.
Other officials said two soldiers were killed in a nighttime attack by militants in the town of Sheikh Zuweyid in northern Sinai. The soldiers were there as part of the offensive.
The officials spoke on condition of anonymity as they were not authorized to publicly brief journalists.
In a statement, Army spokesman Col. Ahmed Mohammed Ali said nine suspected militants were killed on Saturday and nine others detained.
Earlier, another official said "dozens" were wounded in the Sinai offensive. Conflicting casualty figures come from militants taking away the corpses of their comrades and treating their wounded, a security official said. Smoke could be seen rising from villages and troops set up a cordon to prevent militants from escaping as others combed the area, he said.
Troops arrested a number of suspected militants but others managed to escape to mountainous areas in central Sinai, an official said.
In the past, militants used a vast network of underground tunnels linking Egypt with Gaza as a way to escape security crackdowns. However, over the past two months, the military has destroyed more than 80 percent of them, stemming the flow of weapons, militants and goods into Gaza, a territory under an Israeli-imposed blockade.
Sheik Hassan Khalaf, a tribal leader from al-Joura, one of the targeted villages in the area, said the assault was "by far the largest operation we have seen and the one we have been waiting for." As he spoke, the sound of helicopter rotors could be heard.
"Starting today, you will not hear of attacks on army or police checkpoints as before. They either have to flee or get arrested," Khalaf said.
Another tribal leader in the area offered a different account of the operations. He called the raids "arbitrary," citing one incident where army troops attacked the house of a pro-government tribal sheik in the village of al-Dhahir. He spoke on condition of anonymity because of fear of retribution.
A leader of an ultraconservative Salafi group in el-Arish, Hamdeen Abu-Faisal, accused the government of spreading "false and fabricated reports" about targets and causalities in order to rally support from the population.
"There are many question marks over the government-led operations in Sinai," he said. "There is violence and counter violence. But targeting the innocent, demolishing civilians' houses or destroying mosques serves no purpose."