MANILA (AFP) -- Philippine President Gloria Arroyo declared a "state of national calamity" Sunday after giant mudslides triggered by typhoon rains killed hundreds of people.

With the death toll feared to rise to more than 800 people and possibly up to 1,000, Arroyo said the government would continue to mobilize its resources to try to find survivors.

"All resources of the government will continue to be mobilized without let-up as we pin hope against hope on the search of survivors," she said in a statement. "We need to rise up from this trial and help rebuild devastated communities and lives."

The president authorized the immediate release of a billion pesos (20.12 million dollars) to rehabilitate areas affected by super typhoon Durian which devastated the Bicol region last week.

Massive ash and mud slides driven by the torrential rain and wind cascaded down the sides of Mount Mayon volcano, leaving more than 800 people dead or missing, according to the Philippine Red Cross.

The head of the Philippine National Red Cross, Senator Richard Gordon, said declaring a national calamity would help the release of international aid.

In her statement, Arroyo thanked the countries which had offered aid and sympathy. Budget Secretary Rolando Andaya said Arroyo had dispatched him to Bicol to assess the damage "so we will know the resources needed for relief and rehabilitation."

He said the region would need everything from earth-moving equipment and chainsaws to clear roads of rubble and fallen trees as well as fresh water supplies.

Canada announced Saturday that it was donating one billion Canadian dollars (877,200 U.S. dollars) for relief efforts.