Kyamko said civilian volunteers and members of the Citizens Armed Forces Geographical Unit (Cafgu) have been ordered to intensify the village defense system to prevent the bandits from taking more civilian hostages.
The manhunt was further intensified after some villagers positively identified the kidnappers as Abu Sayyaf bandits speaking in Tausug dialect.
The three siblings were kidnapped and beheaded by suspected Abu Sayyaf bandits in Barangay Subilao, a remote village near the city, last June 24.
The victims were identified as brothers Rudy, 24; Wilson, 18; and their sister Rodalyn Mendoza, all residents of Barangay Sibulao, this city.
Their bodies were found decapitated when recovered by soldiers and villagers last Saturday. Their heads were reported as still missing.
The siblings were earlier reported missing for three days after they were snatched by some 60 Abu Sayyaf bandits that reportedly landed in a coastal village here and proceeded to Barangay Sibulao, located some 100 kilometers east of this city in the border of Sibuco and Sirawai towns in Zamboanga del Norte.
Villagers said the siblings were earlier forced by Abu Sayyaf gunmen to act as guides.
The Southcom chief also ordered troops on alert at the boundaries of Sibuco and Sirawai to block the escape of the bandits.
Kyamko declined to give details on the number of soldiers hunting down the bandits but sources and villagers noted the presence of the Army’s Special Forces and Marines in their village.
The military started the search operation based on information from former hostages that some of the remaining bandits led by Abu Sayyaf leader Khaddafi Janjalani fled Jolo to escape pursuing government troops.
The military has been trailing the Abu Sayyaf group who fled from Sulu and Basilan and headed to the mainland of Zamboanga peninsula.
It is not certain whether the bandits landed in the coastal island villages east of this city or on the coastline of Sibuco, Zamboanga del Norte.
The latest abduction and killing comes despite recent government assurances that the Abu Sayyaf had been considerably diminished to only 400 bandits.
The remnants of the bandit group earlier fled to Jolo following the conduct of the RP-US Balikatan joint military exercises in Basilan.
Some Abu Sayyaf fighters fled to nearby Pilas Island, just off the coast of Zamboanga City and Basilan where recent military offensives left 17 of them dead.
The military launched the offensive recently following intelligence reports that Abu Sayyaf leaders are consolidating their remaining forces in the island.
The bandit group, included by the United States in the list of foreign terror organizations, has been loosely linked to the al-Qaeda network of international fugitive Osama bin Laden.
The Abu Sayyaf took more than 100 hostages, including three Americans, among them missionary Gracia Burnham, in a year-long kidnapping spree that ended in June last year.
Mrs. Burnham, whose husband Martin and another hostage, Edibora Yap, were killed during a rescue attempt in Zamboanga del Norte in June last year, has written a book chronicling her captivity in the hands of the enemy.