Cairo: Leading tribes in Egypt’s Sinai have vowed to fight militants there, marking an expansion of a months-long military campaign against radical Islamists in the troubled peninsula.

The decision was made at a tribal meeting earlier this week in North Sinai where the tribes set up an alliance to battle a Daesh-affiliated radical group previously known as Beit Al Maqdis (Partisans of Jerusalem) blamed for a series of deadly attacks mainly against Egyptian security troops, local media reported.

Al Tarabin, a big tribe in North Sinai and a member of the alliance, has said that the action came in response to “atrocious practices” by the extremists.

“What we are doing is an act of self-defence for our people, honour, houses and money, which God and all heavenly and man-made laws make it legal,” Mousa Al Dalh, a leading member of Al Tarabin, said.

He added that the action against militants is arranged in “advance” with the army.

“We’ll continue confrontation until we purge Sinai of terrorists in cooperation with the Armed Forces and the police,” Al Dalh said in a statement without elaborating.

There was no official comment.

Tribal fighters reportedly started attacking militancy strongholds in Sinai.

Pro-government tribal insurgents have driven militants from villages in northern and central Sinai and set their houses and plantations ablaze, independent newspaper Al Masri Al Youm reported on Wednesday, citing tribal sources.

The move came after the militants had killed several tribal civilians, including local leaders allegedly for collaborating with authorities.

Military experts have welcomed the anti-militant alliance, saying it will boost the army’s ongoing crackdown on radicals in the largely desert peninsula.

“Sinai tribes know well the geographical nature of the area,” said Mamdouh Abdul Halim, a military expert. “The tribes’ decision to participate in the war on terrorism came after the hardliners killed several members of these tribes. Thus, the tribes have vengeance and a score they want to settle with these militants,” he added.

“There should be no worries that their action could get out of control because it is being taken in coordination with the state authorities.”

Sinai experienced a security breakdown following the 2011 uprising that ousted long-time president Hosni Mubarak.

The area has seen a surge in fatal attacks targeting security forces since 2013 when the army deposed president Mohammad Mursi of the Muslim Brotherhood following enormous street protests against his rule. Most of the attacks have been claimed by the Sinai-based Beit Al Maqdis that has recently pledged allegiance to Daesh.

In recent months, Egypt has started creating a kilometre-deep buffer zone in North Sinai near the border with the Gaza Strip to facilitate hunting hardline militants.