Six people accused of being "terrorists" have been arrested by Egyptian armed forces in Sinai, after an attack on a police station earlier this week killed 16 border guards, state television reports.
They were arrested during joint army and police patrols searching for criminals in North Sinai province, state news agency MENA reported on Friday.
The arrests came as the army massed troops in the area and Bedouin leaders pledged their help in a meeting with the interior minister.
Military trucks carrying dozens of armoured personnel carriers mounted with machine guns rolled through the town of el-Arish heading eastwards on Thursday, where they claim 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, allegedly in retaliation for an ambush that killed 16 soldiers.
Al Jazeera's correspondent Jamal el-Shayyal, reporting from Sinai, 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 cooperation with the Israelis, in that they should at least be informed," he said.
"The military have sent in the big guns - so to speak - in trying to restore law and order here."
Israel said on Thursday it gave Egypt the go ahead to deploy helicopters in Sinai, easing the restrictions on military presence in the peninsula in a 1979 peace treaty between the neighbouring countries.
At a late night meeting with the interior minister Ahmed Gamal al-Din in el-Arish, roughly 50km west of the Gaza border, Bedouin tribal leaders demanded to see the bodies of the militants reportedly killed on Wednesday.
"We demanded that they present us the bodies, just one or two bodies, so we can be convinced," said Eid Abu Marzuka, one of the Bedouins who took part in the meeting.
Others said they doubted the report, which a military commander in Sinai had confirmed.
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.
"There was a consensus among the tribes to destroy the tunnels. Let [the governing party in Gaza] Hamas be upset, we don't care. Egypt should deal with the Palestinians through the Rafah border crossing," Marzuka said.
"We are against smuggling, and against the siege," he added, referring to the semi-blockade Israel imposed on the enclave after Hamas seized it in 2007.
Hamas said on Friday tha Egypt had temporarily reopened the Rafah border crossing, but only to allow the passage of Palestinians back to the coastal territory.
The interior 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 they say marginalises them.
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"With the help of the people [of Sinai], the mission will succeed," he told reporters after the meeting.
But 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."
Sunday's attack on a border guard outpost in which the fighters killed 16 soldiers before commandeering a military vehicle into Gaza stunned the government and prompted President Mohamed Morsi to sack his intelligence chief and two army generals.
The military said the militants were supported by mortar fire from Gaza during the raid.
After his inauguration on June 30, Morsi has moved to alleviate restrictions on the border crossing with Gaza and met Gaza leader Ismail Haniya. Egypt shut the crossing after Sunday's attack.
Source: Al Jazeera and agencies