(Reuters) -- The South Asian nation has for years been plagued by violence by [extremist] militants who often use suicide bombers and preach that their struggle is a holy war to impose Islamic rule.

Suicide attacks are frequently condemned as fanatical and immoral, especially when civilians are killed, but insurgents view the tactic as their most effective weapon.

Seeking to curb "terrorism" that has resulted in tens of thousands of casualties since the early 2000s, the clerics declared suicide bombings to be forbidden, or "haraam".

"This Fatwa provides a strong base for the stability of a moderate Islamic society," Pakistan President Mamnoon Hussain wrote in the book.

"We can seek guidance from this Fatwa for building a national narrative in order to curb extremism in keeping with the golden principles of Islam."

Foreign and domestic critics of Pakistan's government and military accuse them of cozying up to radical groups for political and military purposes and say the state has for too long turned a blind eye to hate preachers in mosques.

Pakistani officials deny frequent U.S. allegations about collaborating with militant [extremist] proxies in Afghanistan and India, and say vast gains have been made over the past decade against militant outfits such as the Pakistani Taliban.

But privately they also warn any moves against some popular hardline groups based in Pakistan would take a long time and need to be undertaken carefully.

Similar fatwas appear to have yielded scant results in the Middle East where the practice is used by Isis and other militant groups.

The Pakistani scholars, who declared that "no individual or group has the authority to declare and wage jihad (holy war)", said suicide bombings violate key Islamic teachings and were as such forbidden.

The book was prepared by the state-run International Islamic University and Hussain was due at a ceremony to mark the book's release in Islamabad on Tuesday.

(Photo: Iraqis gather at the site of the suicide bomb attacks at Tayran Square in central Baghdad. Photograph: Ali Abbas/EPA)