ALGIERS (Reuters) – Algeria is cracking down on imports of books preaching the ultra-conservative Salafist branch of Islam, officials and industry insiders say, in a step aimed at reining in the ideology's growing influence.

Salafism is a school of Islam that has its roots in Saudi Arabia and emphasises religious purity. Its followers reject the trappings of modern life, including music, Western styles of dress and taking part in politics.

Algeria has for years turned a blind eye to Salafism, but recent shows of strength by its followers — including some Salafist clerics refusing to stand for the national anthem — have focused official attention on the group.

Customs officers and officials from the ministries of religious affairs and culture have been given instructions to enforce more tightly an existing list of banned literature, and have been policing industry events where books are on sale.

"This year, instructions to pay attention to Salafist literature were tough," Mohamed Mouloudi, a publisher and importer of religious books who opposes the Salafist school of Islam, told Reuters.

Hundreds of Salafists, with their trademark beards and white "khamis", or gowns, visited the annual Algiers International Book Fair earlier this month. They usually use the event to buy up religious literature in bulk to re-sell.

But customs officers present in large numbers at the fair prevented them from doing business as usual. Groups of uniformed officers patrolled vendors' stands checking the books on sale against their list of banned literature.

The officers also intercepted any buyers who had bought several large plastic bags of books. Ninety percent of the people stopped had beards and were wearing khamis gowns, according to a Reuters reporter there.

"Those who resell are visible because they carry heavy bags full of books. Our job is to seize the books and give them one copy of each," a customs officer, who asked not to be named, told Reuters at the book fair.