Rights activists reported last month that Egyptian police had detained 2500 people in Sinai and tortured many of them in the hunt for those behind the 7 October bombings targeting Israeli tourists in Taba and two other resorts, which killed at least 34 people.
Egypt's official Middle East News Agency reported the news from Sinai on Monday.
It said the tribes signed a letter affirming "their complete commitment not to shelter any person wanted by security", and said they would cooperate by reporting anyone under suspicion.
The security pledges were in a letter signed by tribal shaikhs and other notables at a meeting in Ras al-Sudr in Sinai.
Although it is not uncommon for tribal and community leaders to vow allegiance to President Husni Mubarak, activists say such acts are usually associated with events such as new terms of political office and rarely include pledges to help security.
Ahmad Saif al-Islam Hamad, from the Hisham Mubarak Law Centre, said the oath of allegiance appeared "directly linked" to the Sinai bombings and their aftermath, and might in part be an attempt by the tribes to ease the recent security campaign.
Thirty four people were killed in
the resort attacks
The report by human rights groups in November, which quoted victims and witnesses, said police had hanged men by their arms for hours, with electrodes attached to their toes, and burned their skin with devices that looked like oven lighters.
It also said security forces had taken 140 Sinai women hostage in the hope their families would turn in their menfolk.
The government says it does not condone torture and punishes torturers when it comes across abuses.
Egypt has blamed the blasts on a Palestinian and three Sinai Bedouin, saying there was no indication the bombers were linked to al-Qaida, as Israel and the United States have suggested.
Most of the alleged bombers and accomplices come from al-Arish in north Sinai, close to the border with the Gaza Strip, the government said.