JERUSALEM - Israel on Thursday gave Cairo its approval to deploy helicopter gunships in the neighbouring Sinai peninsula, where Egypt's military has vowed to crush Islamic militants, an Israeli official said.

The official, on condition of anonymity, said that Israel's 14-member security cabinet had agreed to a temporary easing of the terms of a 1979 peace treaty which limits Egypt's military deployment in the Sinai.

The decision came a day after the Egyptian military said it had already deployed attack helicopters in raids that killed 20 militants in the territory.

The operation was launched after gunmen on Sunday killed 16 Egyptian guards near the border and tried to storm southern Israel.

They raided a border guard base under the cover of mortar fire and commandeered a military vehicle into the Jewish state before they were halted by an Israeli helicopter strike.

Israel handed over to Egypt six "completely charred" bodies that were in the armoured personnel carrier driven into the country before being destroyed, an Egyptian medical official said.

Meanwhile, Egypt's army massed troops in Sinai on Thursday to quell increasingly deadly Islamist militants as 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, where Bedouin Islamist militants have established a presence in villages near the border with Gaza.

At a late night meeting with the interior minister Ahmed Gamal al-Din in El-Arish, roughly 50 kilometres (30 miles) 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 Islamist rulers of Gaza) Hamas be upset, we don't care. Egypt should deal with the Palestinians through the Rafah border crossing," said Marzuka.

"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.

The interior minister said his forces and the military would defeat the militants with the help of the Bedouin tribes, which have been hostile toward the central government they say marginalises them.

"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 said, 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 militants killed 16 soldiers before commandeering a military vehicle into Israel 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 inauguation 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.

In the Gaza Strip, where Egypt closed its Rafah border crossing after the attack, the Hamas interior ministry said Palestinians returning from Egypt would be allowed passage from Friday.