Israel's defence minister on Tuesday confirmed giving Egypt the go-ahead to deploy two battalions in Sinai to tackle militants in a region where deployments are restricted by treaty.
Speaking to army radio, Moshe Yaalon said he had approved a request from the Egyptian army to station one battalion at El-Arish in the north of the peninsula and one at Sharm al-Sheikh in the south.
"Egypt presented us over the last few days with requests to allow additional forces to enter to combat terrorism," Yaalon said.
"When these forces are involved in the fight against terrorism, as long as we're consulted and it does not violate the treaty between the two countries, we accept their requests so they can remove the terror threat from Sinai," he said.
Israel already gave its backing earlier this month to Egypt's deployment of a first batch of troop reinforcements to the Sinai, where deployments are restricted under the terms of the 1979 peace treaty between the two neighbours.
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"The Egyptian military activity in the Sinai is coordinated with Israeli security elements and authorised at the most senior levels in Israel, in order to contend with security threats in the Sinai that pose a threat to both Israel and Egypt," an army statement said at the time.
The Egyptian army is preparing to go on the offensive against Islamist militants in the Sinai who have escalated attacks since president Mohamed Morsi's overthrow on July 3.
Over the past two weeks, militants have launched almost daily attacks on troops and police in the peninsula, killing several members of the security forces and two Egyptian Christians.
At dawn on Monday, militants killed three workers from a cement factory in an attack on the bus in which they were travelling in El-Arish.
A senior Egyptian military official confirmed to AFP on Monday that the army "will carry out an operation" in the Sinai, without giving further details.
The army knew the militant leaders by name and their location, he said, adding that most of the militants "live with their family, in villages".