In a renewed warning that supersedes a March 23 advisory, the State Department urged Americans to travel to the Philippines only if necessary because of heightened threats to Westerners.
Those who do go should take vigilant security precautions and remain aware of the continued potential for terrorist attacks, the department warned.
"Terrorist groups including Jemaah Islamiyah and the Abu Sayyaf Group continue to plan multiple attacks throughout the Philippines as do some radical insurgents who have broken away from Moro groups," the department said.
It said explosive devices have been placed in shopping malls, on public transportation, at airports and port facilities, in places of worship, and in other public areas resulting in numerous deaths and casualties.
Areas in the southern Philippines were particularly at risk of attack.
It noted that because security has increased at official US facilities, terrorists might seek softer targets such as places where Americans and other Westerners might live, congregate, shop or visit.
US ambassador Kristie Kenney earlier said the Philippines remains relatively peaceful but should stay on alert against possible terrorist attacks.
"The Philippines, like so many countries in the world, is very concerned and worried about terrorism threats and I think we’re working very closely together (with the Philippine government)," she told reporters Friday.
Kenney explained that the State Department’s travel advisories "are for countries throughout the world and it helps our citizens travel as safely as possible," adding that Washington will update the advisory "as the situation requires."
The Philippines has objected to past US travel warnings, saying they do not reflect efforts and gains made by local security forces in the government’s own campaign on terrorism.
The Philippines is considered one of the weakest links in the US-led global campaign on terrorism.
The Philippines and the United States have worked together in fighting both local and foreign Muslim extremists allegedly linked to such groups as Jemaah Islamiyah and the al-Qaeda terrorist network.
The United States considers the al-Qaeda-linked Abu Sayyaf, the Communist Party of the Philippines and its armed wing, the New People’s Army as terrorist organizations.
The Abu Sayyaf is notorious for abducting foreigners for ransom while the Communist Party of the Philippines has been fighting an insurgency for over 30 years.
A suspected NPA threat prompted the US Embassy in Manila to close for two days last December.
Manila and Washington recently concluded a security arrangement that would widen US troop involvement in dealing with threats in the Philippines not covered by the two countries’ 1951 defense treaty, including terrorism.
The arrangement also allows the US military to help in disasters.
President Arroyo is one of Asia’s most vocal backers of Washington’s war on terror and has allowed US forces to train and arm Philippine troops battling al-Qaeda-linked militants in parts of Mindanao, the scene of decades-old separatist Muslim uprisings.
The Philippine government is in talks with the United States seeking more medical missions from the US military in areas known to be terrorist breeding grounds following the successful humanitarian mission in the south of the US military hospital ship Mercy. — With Pia Lee-Brago, AP, AFP