EL-ARISH, Egypt — Egypt’s President Mohammed Morsi took a helicopter ride along the Egypt-Israel border, and broke the daily Ramadan fast with Egyptian troops on Friday evening, underlining his determination to reassert sovereignty in the Sinai five days after terrorists killed 16 Egyptian troops there and then smashed across the border into Israel before being thwarted.

Morsi, who was joined by the head of the Egyptian Armed Forces, General Mohammed Hussein Tantawi, came to Sinai to inspect the status of the Egyptian army’s anti-terror operation there. Egyptian forces are preparing to create a large-scale operation center near el-Arish Saturday. Approximately 50 tanks, helicopters, and units specializing in explosives crossed the Suez Canal into Sinai Friday.

Engineering teams blocked more than 100 underground smuggling tunnels with sand and cement to prevent future terror infiltrators from Rafah on the Egyptian-Gaza border.

Morsi, who has fired a number of intelligence and military chiefs since Sunday’s attack, has ordered a military crackdown on terror cells in the Sinai in the last four days. He said Friday that another major military operation against the terror groups would begin in the central Sinai on Saturday.

Egypt says it has killed dozens of suspected Islamist terrorists in the past few days, utilizing air and ground forces against the cells. It has also sought the extradition from Gaza of several Hamas and Hamas-affiliated terror chiefs suspected of involvement in Sunday’s terrorist attack on an Egyptian border position and subsequent foray into Israel across the Kerem Shalom Border crossing.

Egyptian troops and security forces on Friday detained nine Islamic extremists in northern Sinai believed to be behind Sunday’s attack, a security official said.

Islamic militant groups have become bolder and grown in numbers since the ouster last year of Hosni Mubarak.

So far the effectiveness of the 4-day-old Egyptian military operation is not clear. Despite the influx of troops, militants have continued low-level attacks on Egyptian troops and security forces. One famous checkpoint on the road linking the Rafah border town with the city of el-Arish comes under attack almost daily. Officials say that militants open fire at night, engage in brief firefights then flee.

In a raid early Friday morning, troops stormed a house in Sheik Zweid, close to the Rafah border crossing with the Gaza Strip, and caught the nine suspected terrorists while they were asleep. Among them was Selmi Zeyoud, whom the official described as a “dangerous element” and a brother to a slain jihadist.

The official said the nine were suspected of involvement in the assault last Sunday, in which gunmen stormed an army checkpoint by the borders with Gaza and Israel, and killed 16 soldiers as they were breaking their daily fast for the holy month of Ramadan with a sunset meal. The attackers then commandeered an armored vehicle, which they later used to storm across the border into Israel where they were hit by an Israeli airstrike.

Large swaths of northern Sinai have plunged into lawlessness following the ouster of Mubarak in last year’s uprising, and weapons smuggled from Libya have found their way into militants’ hands. The weapons and the security vacuum fueled the rise of al-Qaida-inspired militant groups which have staged several cross-border attacks on Israel.

Security officials estimate the number of militants in northern Sinai at some 1,500 but some Bebouin tribal leaders have put the number in the thousands. One prominent tribal chief, Awda Abu-Malhous, put it as high as 10,000.

The military sent tanks and troops to the peninsula to combat the terror groups. However, witnesses say the offensive has been limited to a few raids on houses of suspected militants. The Al-Ahram newspaper and other state-run papers reported Friday that 60 “terrorists” have been killed in airstrikes. However, medical officials say no bodies reached el-Arish’s only hospital.

Officials said earlier that along with the offensive, Egypt is going after an elaborate network of underground tunnels used to smuggle weapons, militants and goods between Sinai and Gaza. Al-Ahram reported that 150 tunnels have been destroyed. Resident in the area said the tunnels targeted were not the most active ones.

The local Bedouin population is largely resentful of the central government over years of discrimination, marginalization and heavy-handed security sweeps under Mubarak. Some have nonetheless helped the military, though many are fearful of risking their lives if they help security forces and provide tips on the militants — many of whom are Bedouins — after one tribal leader was shot dead two months ago for cooperating with the police.

The weekend attack has rattled the Egyptian government, the military council and Morsi, who fired the chief of intelligence and other top officials in an apparent attempt to defuse public discontent.