The field and surrounding areas in the South China Sea off Palawan island were "reserved as safety and exclusion zones" to protect the environment, secure the infrastructure from damage and ensure that the supply of gas will not be hampered, a DND statement said.
Under a presidential order, unauthorized vessels and aircraft will not be allowed in the exclusion zone and drilling and explosive activities will also be restricted.
Trawl fishing and other fishing methods using weights and anchors and the laying of undersea cables and pipelines in the area are also prohibited.
President Arroyo inaugurated the $4.5-billion Malampaya project last Tuesday. An undersea pipeline delivers the gas to power plants in Batangas.
The project is expected to raise $3 billion in government revenues in the next 20 years and significantly cut oil imports.
Malampaya has proven reserves of 78 billion cubic meters and 85 million barrels of condensate. It is operated by a unit of Royal Dutch/Shell. - Paolo Romero