* Violence has grown in Sinai since Mubarak overthrow
* Egypt says some militants hail from Gaza
* Four suspects caught close to strategic gas pipeline
By Marwa Awad
CAIRO, Aug 16 (Reuters) - An army crackdown on armed groups in Egypt’s lawless north Sinai has netted four Islamist militants as they prepared to blow up a gas pipeline in the city of el-Arish, security sources said on Tuesday.
The military operation -- dubbed Operation Eagle -- began this week with the aim of quelling an increase in attacks on security forces in Sinai since the overthrow of President Hosni Mubarak in a popular uprising in February.
Sinai’s population has a history of resentment towards officials from Cairo, who have struggled to stamp their authority on the desert region bordering Israel.
Those efforts have been hampered partly because of limits on any military build-up there agreed under the 1979 Camp David accord between the two neighbours.
An intelligence official said the initial investigation that prompted Operation Eagle had linked the four militants to an assault on a police station in el-Arish on July 30 in which an army officer, two policemen and three civilians died.
Around 100 armed men rode through the town in cars and on motorcycles that day, waving flags with Islamic slogans before attacking the police station.
“The militants arrested today were linked to that Islamist militant group,” the intelligence officer told Reuters.
Other suspects are suspected of links to al Qaeda while others are members of Palestinian armed groups from Gaza to the north who managed to enter Egypt through tunnels, he said.
The four suspects, caught in el-Arish near a gas pipeline linking Egypt to Israel, possessed explosives and weapons, a security source in the town said.
They were the second arrests since the army operation began. On Monday, troops attacked militant hideouts, killing one gunman and arresting 11 militants, according to security sources.
“Some of these militants hail from the Gaza strip and had infiltrated through tunnels linking Gaza with Rafah (on the border),” the intelligence officer said.
He said an estimated 1,200 to 1,300 armed militant groups and jihadists were making use of the security vacuum left by Mubarak’s overthrow.
Many have formed alliances with armed Bedouin tribes who have strongholds in the mountains of Sinai. (Additional reporting by Yusri Mohamed in Ismailia; Writing by Marwa Awad; Editing by Tom Pfeiffer)