"The banned organizations are not allowed to visit flood-hit areas," Interior Minister Rehman Malik told Reuters. "We will arrest members of banned organizations collecting funds and will try them under the Anti-Terrorism Act."

Pakistani President Asif Ali Zardari warned on Thursday that militants were trying to exploit the floods to promote their agendas -- as they did after a devastating earthquake in Kashmir in 2005.

Islamist charities have moved swiftly to fill the vacuum left by a government overwhelmed by the scale of the disaster and struggling to reach millions of people in dire need of shelter, food and drinking water.

It would not be the first time the government has announced restrictions against charities tied to militant groups, but critics say banned organizations often reemerge with new names and authorities are not serious about stopping them.

Nearly three weeks of floods have made more than four million Pakistanis homeless, making urgent the critical task of securing enough aid.

Reuters