Saturday’s blast was the third in Sinai since police last week launched a large-scale search operation for the group, thought to be Sinai Bedouin under the influence of militants.

The security sources, who asked not to be named, identified the officer as Lieutenant-Colonel Rushdi el-Sayed and the tracker as Hassan Eid, a Sinai Bedouin.

The landmine exploded near Mount Halal, the area which has been at the centre of the search, the source added.

Mount Halal is 892m high and about 60km south of the Mediterranean town of el Arish, the home area of several named bombing suspects.

Red Sea bombings

Police say they were looking for the remaining members of the group that killed 98 people in bombings in the Red Sea resorts of Taba in October and Sharm al-Shaikh in July.

Landmine explosions in Sinai on Wednesday and Thursday damaged three police vehicles, killed two police officers and injured at least five officers and a civilian.

Premier Ahmed Nazif said police were
working on two Sinai bomb theories

Thousands of police with armoured vehicles are taking part in the operation, security sources said last week.

Parts of Sinai still have landmines from wars between Egypt and Israel, but the number of explosions this week suggests the fugitives laid them recently, a security source said.

Police held 34 local people for questioning on Friday, but it was not known whether they were part of the group, the source added.

Social factors

Egyptian Prime Minister Ahmed Nazif said the government was looking at social factors in north Sinai that might have contributed to inspiring people to become bombers in Sharm al-Shaikh.

"We need to see why this happened and how this happened," he told Tuesday's New York Times. "Is it just people frustrated, or are they people with connections?"

He said the authorities were working with two theories about who was behind the Sharm al-Shaikh bombings - that security forces were so aggressive after the Taba blasts that they prompted retaliation by locals or that the group had international connections such as to al-Qaida.