EL-ARISH - Gunmen attacked a checkpoint in Egypt's Sinai Peninsula overnight, causing no casualties, as the army massed troops to quell increasingly deadly Islamist militants, a security source said Friday.
At the same time, security sources said six "terrorists" had been arrested in the Sinai.
And Egypt temporarily reopened the Rafah border crossing into the Gaza Strip, which was closed after militants attacked troops on Sunday and killed 16 soldiers.
There were no further details on the overnight attack outside the town of El-Arish in a region that has been increasingly on edge since Sunday's raid.
State news agency MENA said six "terrorist elements," who a security source told AFP were known Islamist hardliners suspected of belonging to a jihadist group, had been arrested during patrols in North Sinai province.
On Thursday, trucks carrying dozens of armoured personnel carriers mounted with machineguns rolled through El-Arish heading to the east, where Bedouin Islamist militants have established a presence in villages near the borders with Gaza and with Israel.
El-Arish and its environs were calm on Friday, an AFP journalist said.
A number of armoured vehicles had taken up positions in the town, and a tank sat behind a barrier of sandbags painted with Egypt's black, white and red national colours on which was written the slogan "victory or death."
The build-up comes after state television reported that military helicopters and soldiers killed 20 militants on Wednesday in the first such operation in the Sinai in decades, in retaliation for the raid.
Israel said on Thursday it gave Egypt the go-ahead to deploy helicopters in Sinai, easing the restrictions on military presence in the peninsula set by a 1979 peace treaty between the neighbouring countries.
At a late-night meeting with 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 Bedouin 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 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 virtual blockade Israel imposed on the enclave after Hamas seized it in 2007.
On Friday, Egyptian state television said it had been decided to reopen the Rafah crossing in the Gaza direction only, to allow people in Egypt to return home. Among them were Palestinian Muslims who were returning from pilgrimage to Saudi Arabia.
It did not say how long the "exceptional" opening would last.
Egypt closed the crossing after Sunday's raid, in which militants also commandeered a military vehicle and crossed the border into Israel before being killed.
The military said the militants were supported by mortar fire from Gaza during the raid.
The Sunday attack stunned the government and prompted Morsi to sack his intelligence chief and two army generals.
The interior minister said his forces and the military would defeat the militants with the help of the Bedouin tribes, who have been hostile toward the central government which 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 told AFP, speaking on condition of anonymity because he was not authorised to speak to media. "The geography, the desert and mountains, will make this difficult."