Based on their preliminary findings, detectives suspect these Qawmi and Forkania madrasas are the breeding grounds and safe hideouts of Islamist militants.

Sources said some 500 madrasas in Tangail, Jamalpur, Moulvibazar, Sunamganj, Sylhet, Narail, Narsingdi, Natore, Naogaon, Rajshahi, Chapainawabganj, and Cox's Bazar will be watched over.

The government has recently issued strict directives to the home ministry to trap militants in the wake of rise of militancy in the country.

A ruling party lawmaker speaking anonymously said a certain section of madrasas are producing these elements, who are now carrying out violent acts to establish so-called Islamic rule.

Many of these madrasas do not even have the approval of the government. The law enforcers should closely monitor activities in these unapproved Islamic educational institutions, he added.

A highly placed source in Detective Branch of police said lawmakers of different parties have set up a large number of madrasas in their electoral areas to create "vote banks".

Establishment of madrasas has marked a sharp rise during the reigns of the BNP and the Awami League in the last 14 years, the DB official added.