Egypt's air force pounded militant targets in northern and central Sinai early on Saturday, the military said, the second day of an assault to try to crush an insurgency that has killed hundreds of people since 2013.
The Egyptian army announced on Friday the start of a wide-scale military operation in the central and north Sinai Peninsula, in addition to other areas in the country.
President Abdel Fattah al-Sisi, who is seeking re-election in March, ordered the armed forces in November to defeat militants within three months after an attack on a mosque killed more than 300 people.
The military said its warplanes struck "terrorist concentrations and hideouts" in northern and central Sinai through the night and into the early hours of Saturday, targeting weapons warehouses and logistics support areas.
On the ground, special forces, working with police, conducted raids inside cities in Sinai to seize militants, military spokesman Colonel Tamer al-Rifai said in a statement.
Sixteen militants were killed and 4 others arrested in a major crackdown launched by Egypt on Friday, the Egyptian army said in a statement carried by state TV early on Sunday.
Another 30 suspects were arrested, it said.
Border guards and naval forces were securing the Suez Canal to make sure navigation through the international waterway was not affected, the statement said.
It gave no details on any casualties in the operation or any figures on the number of people arrested, but said the assault would continue.
"The armed forces and the police assert their determination to uproot terrorism and to achieve peace and stability," Rifai said, according to the statement.
Apart from Sinai, the Egyptian army said the operation would also cover parts of the Nile Delta and the Western Desert, where other militants have waged attacks, some believed to be staged out of neighbouring Libya.
State television said on Friday that all schools in North Sinai had been ordered shut from Saturday until further notice.
The Suez Canal Authority chairman said the waterway was operating normally. Forty-eight ships passed through the canal on Saturday amid extensive security measures, the authority said.
The success or failure of the military's latest push will most likely not affect the result of the March 26-28 election. Sisi is widely expected to win as all opposition figures thought to pose a serious challenge to him have pulled out of the race.