ISLAMABAD: From calls for blood revenge to codes of honour, centuries-old tribal laws are complicating the sweep for Al Qaeda fighters and the hunt for Osama bin Laden on the Pakistan-Afghanistan border.

Several thousand Pakistan army troops have encircled several hundred foreign militants, including Al Qaeda fighters, holed up in mud fortresses in South Waziristan - a perilous no man's land bordering Afghanistan.

But in the mountainous area where tribal elders administer justice by ancient codes, the authorities need to tread carefully or risk inflaming their own people, experts say.

The 10-day confrontation had already stirred a backlash connected to one tribal law known as "badal", or an obligation of revenge that can last for generations, said Ibrahim Shinwari, a tribesman from Peshawar.

Ibrahim Shinwari said he believed a rocket attack on Peshawar on Tuesday was an expression of "badal" in retaliation for the death of 26 civilians in the fighting.

Nearly 100 people have died in 10 days of sporadic fighting in South Waziristan, the largest and one of the poorest of seven tribal agencies whose dusty villages are a haven for Taliban and Al Qaeda fighters.

Some 60 soldiers, 11 foreign militants and 26 civilians, most of them women and children, have died so far. Unless the army operation ends soon, the risks grow of a revolt among the tribes spreading beyond South Waziristan into areas where sympathy for the Taliban runs high, tribesmen say.

BLOOD REVENGE: "Badal has already started and there is a danger it could spill into other tribal territories," Ibrahim Shinwari said. Hoping to avoid inflaming the situation further, the advance on South Waziristan has slowed in recent days to allow tribal elders to negotiate with militants.