Egyptian tanks were rolling into a town near Gaza's border on Saturday for an anticipated operation against militants who attacked a gas pipeline to Israel and police stations, security officials said.
The officials said the tanks and more than 1,000 soldiers and policemen, deployed on Friday and Saturday, would try to restore order to a lawless section in the north of the Sinai peninsula, and then move southwards to a mountainous region where armed outlaws were hiding.
Tanks and armoured vehicles were stationed in El-Arish, 40 kilometres (25 miles) from the Gaza Strip, where Islamist militants attacked police stations two weeks earlier, killing a military officer and three bystanders.
"The forces that have arrived will participate in several surprise raids to arrest wanted men and those who participated in the attack (on the police station)" one security official said.
They were also seeking militants behind five bombing attacks this year on a pipeline that exports gas to Israel.
The operation will start in El-Arish, and then roll into the neighbouring Sheikh Zuwied, where authorities believe Islamist militants are hiding out, and the Rafah border town, the officials said.
The operation, codenamed "Eagle," would then extend to mountainous central Sinai, long a safe haven for Bedouin outlaws.
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"These reinforcements have been sent to aid forces already stationed, to restore security, arrest those behind the El-Arish attacks and capture outlaws in the mountains," a senior security official told AFP.
He refused to say how they intended to storm the formidable mountain hideouts. "This is a plan put together in coordination with the military and it will succeed," he added.
The officials declined to give a precise number for the troops involved. A 1979 peace agreement with neighbouring Israel limits the number of Egyptian soldiers allowed in the peninsula.
The governor of North Sinai, Abdel Wahab Mabruk, denied the increased forces would carry out raids. "They are here for protection, and to repel any further attacks," he told AFP.
He acknowledged that there was no police presence in areas of Sinai, such as the town of Sheikh Zuweid, since the interior ministry largely collapsed during a January-February uprising which ousted president Hosni Mubarak.
But he said the security forces would not try to comb the area. "This is not a war."
However, the security officials, who spoke on condition of anonymity because of the sensitivity if the issue, said the raids were imminent.
Sinai, home to some of the country's most lucrative tourist resorts, also has a largely marginalised and poor Bedouin population with a history of tensions with the Cairo government.
Islamist Bedouin militants were blamed for a series of massive explosions in tourist resorts between 2004 and 2006 that killed dozens of Egyptians and foreigners.
Some of the militants arrested after those attacks fled prison during the January revolt when police abandoned their posts.