With an insurgency threatening its sensitive border with Israel, Egypt's military is preparing to go on the offensive against Sinai militants who have escalated attacks since president Mohamed Morsi's ouster.
During the past two weeks, militants have launched almost daily attacks on military and police forces 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 the north Sinai town of El-Arish.
A senior military official confirmed to AFP that the Egyptian 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".
The army would approach the operation carefully, he said, as it is keen to avoid friction with civilians, "but we don't want things to take us to a stage that affects our national security".
Analysts said the Sinai violence could be down to Islamist extremists seeking to take advantage of the political insecurity in the country after Morsi's ouster.
Shadi Hamid, director of research at the Brookings Doha Center, said the attacks could be by militants already sworn to fighting the state.
Militants "who are already radical are emboldened and see it as an opportunity to move more aggressively," he said.
Hamid said there was already sympathy in the Sinai for agitation against the government.
"When there was significant anger over Morsi's ouster, they took advantage of that situation," he said.
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Armed extremists in north Sinai could also exploit the military's focus on securing the political transition, Oliver Coleman, a senior risk analyst for London-based Maplecroft, said in a report.
Coleman added that "it is possible, though at this point not especially likely, that Sinai militants will link up with newly disaffected Islamists in the Nile Valley".
However, he warned it was "all the more likely if (Muslim) Brotherhood members continue to be arrested or the group is excluded from the political process".
The Egyptian army has called on the Brotherhood, the group from which Morsi hails, to participate in the political transition it has launched since ousting the Islamist president on July 3.
But the influential Islamist movement has refused and insisted on Morsi's reinstatement, accusing the army of plotting a "coup against him".
In what appeared to be a message to the Brotherhood, army chief General Abdel Fattah al-Sisi said on Sunday that he hoped all political parties were aware that "the opportunity was available to all political sides", of all ideologies.
Controversy erupted in Egypt last week over alleged links between the Brotherhood and armed groups in the Sinai.
Television stations broadcast verified footage of one of the Islamist group's senior leaders Mohammed al-Beltagui saying "what is happening in the Sinai will stop the second president Morsi returns" to office.
Beltagui qualified his statement by saying the Brotherhood did not call the shots in the Sinai.
Opponents of the Brotherhood said the video was evidence of the strong links between the Islamist group and militants in the restive peninsula.
Beltagui categorically denied ties between his organisation and the Sinai violence. In comments to Al-Jazeera, he said the Brotherhood has "no relation with what is happening in the Sinai".