Nationals of nine countries which US intelligence authorities identified as "sponsors of terrorism" are under tight watch by immigration officers at the Ninoy Aquino International Airport and other ports of entry.
Immigration Commissioner Rufus Rodriguez identified the nine countries as Libya, Syria, Iran, Iraq, Cuba, Sudan, North Korea, Afghanistan and Pakistan.
All these countries, except for Pakistan and Afghanistan, have long been tagged by US intelligence as providing arms, logistics, training, and funding support for foreign extremist groups, he added.
Rodriguez said the Philippines may now be a favored destination of terrorists following the escalation of hostilities between government troops and separatist guerrillas in Mindanao.
The military reported spotting several "Arab-looking foreigners" conferring with leaders of the Moro Islamic Liberation Front (MILF) in a rebel camp in Maguindanao a few months ago.
Last month, police and immigration agents arrested an Iraqi, Naef Menaor Govin Famez, after he tried to sneak into the country with a tampered Saudi Arabian passport.
Intelligence sources said Famez came to the Philippines to contact Pandu Tudhawinata, an Indonesian passport holder, who is believed to be involved in providing arms and training to separatists in Mindanao.
Police and immigration agents arrested Tudhawinata and a certain Abdesselem Boulanovar, an Algerian national, last December.
The two were allegedly involved in destabilization plots and secret operations in Mindanao.
Rodriguez ordered immigration officers to arrest and deport any foreigner who is suspected of being a terrorist.