Egyptian President Mohamed Morsi has visited the city of el-Arish in North Sinai for the second time since a surprise attack near the Rafah border crossing nearly a week ago that killed 16 Egyptian soldiers.
During his visit on Friday, the president promised to use "a grip of steel to stop the criminals".
"We will not rest until we finish our mission," Morsi said, addressing a cheering crowd, referring to a major Egyptian military operation in the Sinai Peninsula in retaliation to the attack, aimed at stamping out hostile groups.
The recently-elected Morsi and the country's longtime defence minister Field Marshal Hussein Tantawi broke their dawn-to-dusk fast in a symbolic gesture with soldiers in northern Sinai.
According to a security official, Egyptian troops and security forces on Friday detained a number of suspected "terrorists" in the area believed to be behind the attack.
At least six people were arrested in northern Sinai, state news agency MENA reported. They were arrested during joint army and police patrols searching for criminals in the province, the agency said.
The arrests were in response to 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 armoured vehicle, which they later used to storm across the border into Israel where they were hit by an Israeli airstrike that killed at least six fighters.
The Egyptian army has since massed troops in the area and Bedouin leaders on Friday pledged their help in a meeting with Ahmed Gamal al-Din in el-Arish, the interior minister.
During the meeting with the minister, the tribal leaders said they had agreed to help the military and police to restore security in the lawless peninsula and close down tunnels used to smuggle contraband and weapons to the Palestinian Gaza Strip.
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The minister said his forces and the military would defeat the groups responsible for the violence with the help of the Bedouin tribes, which have been hostile toward the central government which they say marginalises them.
"With the help of the people [of Sinai], the mission will succeed," Din told reporters after the meeting.
Another senior security official stationed in Sinai acknowledged that they faced an elusive enemy that had the advantage of the peninsula's formidable mountain and desert terrain.
"It will be gradual," he told the AFP news agency, speaking on condition of anonymity because he was not authorised to speak to media. "The geography, the desert and mountains, will make this difficult."
Military trucks carrying dozens of armoured personnel carriers mounted with machine guns rolled through el-Arish heading eastwards on Thursday, where they claimed Bedouin "Islamists" with links to the attacks have established a presence in villages near the border with Gaza.
The build-up came after state television reported that military helicopters and soldiers killed 20 people on Wednesday in the first such operation in Sinai in decades.
Al Jazeera's Jamal el-Shayyal, reporting from Sinai on Friday, said that it was the first Egyptian military operation in the Sinai since the peace treaty with Israel in 1979.
"The treaty says that any sort of military operation inside the Sinai should be done in collaboration, or at least in c-ooperation, with the Israelis, in that they should at least be informed," he said.
Israel said on Thursday it gave Cairo the go ahead to deploy helicopters in Sinai, easing the restrictions on Egypt's military presence in the peninsula in a 1979 peace treaty between the neighbouring countries.
So far the effectiveness of the 4-day-old operation is not clear.
Despite the influx of troops, fighters 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 fighters open fire at night, engage in brief firefights then flee.
Some Sinai residents have also been sceptical about the army's reported crackdown, saying they had seen no sign of anyone being killed in what they described as a "haphazard" operation.
Officials said earlier that along with the offensive, Egypt was going after an elaborate network of underground tunnels used to smuggle weapons, fighters and goods between Sinai and Gaza, the Palestinian enclave under a longtime Israeli blockade.
Egypt's Al-Ahram reported that 150 tunnels have been destroyed. Residents in the area said the tunnels targeted were not the most active ones.
Meanwhile, on Friday Hamas, which controls Gaza, said that Egypt had temporarily reopened the Rafah border crossing, but only to allow the passage of Palestinians back to the coastal territory.
Source: Al Jazeera and agencies