More than a dozen armed men abducted a naturalized American, her teenage son and Filipino nephew before dawn Tuesday from a southern Philippine island near a stronghold of al-Qaida-linked militants, officials said.
Suspicion fell on the notorious Abu Sayyaf, which has been blamed for ransom kidnappings, beheadings and bombings in the last two decades, or a Muslim rebel commander whose group has been linked to previous abductions.
The 400-plus Abu Sayyaf militants, who are fighting for an Islamist state in the predominantly Christian nation, are holding three other kidnap victims, including a child, as part of desperate efforts to raise funds, according to the Philippine army.
The assailants seized Gerfa Yeatts Lunsmann, her 14-year-old son and 19-year-old Filipino nephew from a house in Zamboanga city's Tictabon island village, then fled with their captives in two motorized boats, said police Senior Superintendent Edwin de Ocampo.
No contact or ransom demand has been made by the abductors, and their identities remain unconfirmed, de Ocampo said.
It happened near Basilan Island, the birthplace and stronghold of the Abu Sayyaf militants, about 550 miles (880 kilometers) south of Manila.
The largest Muslim separatist group, Moro Islamic Liberation Front, is present in the area but it has been negotiating with the government and a cease-fire has largely held for several years.
However, the military said a separatist Moro commander identified as Waning Abdulsalam may have been responsible. Rebel spokesman Von Al Haq said his group would investigate but that it has no such report and will not tolerate criminal activities.
Police earlier said the woman was a Filipino married to a German and the family lives in the U.S. state of Virginia.
But army Col. Buenaventura Pascual, commander of an anti-terrorist task force in Zamboanga, said his men on Tictabon Island saw the U.S. passports of Lunsmann and her son, showing they were American citizens.
The State Department said it was aware of reports that two U.S. citizens have been abducted and was working with Philippine authorities. The department said it was concerned about the individuals' safety and well-being, and called for their immediate release and prosecution of those responsible.
Lunsmann, 50, was originally from Basilan and her previous name was Jerpa Usman, Philippine police and military officials said.
Pascual said the woman's husband is apparently an American citizen of German ancestry. He did not accompany his wife and son, who arrived in the Philippines two weeks ago to visit relatives.
"We have deployed troops to track down the victims," Pascual said.
Presidential spokesman Edwin Lacierda said the local crisis committee was convened and that police and the military were trying to rescue the victims and capture the culprits.
Military spokesman Lt. Col. Randolph Cabangbang said intelligence reports showed the victims may have been brought to Basilan's Tuburuan township.