Meanwhile, negotiations for the release of Fr. Giuseppe Pierantoni shifted into high gear following reports that the hostage has fallen ill.
The Italian priest has reportedly contracted amoebiasis and is in danger of dehydration.
Abdul Makmud Mohammad became the third suspect to fall in connection to the abduction of the 44-year-old missionary last Wednesday shortly after the victim officiated Mass at his parish church in the coastal town of Dimataling in Zamboanga del Sur.
The first suspect, identified as Akiddin Abdusalam, was killed in an escape try last Thursday as he led soldiers to their hideout on an island off Dimataling.
Brig. Gen. Angel Atutubo, commander of Task Force Giuseppe, said Mohammad had admitted acting as lookout for some 15 heavily armed members of the Pentagon gang who snatched the Italian priest.
Atutubo said Mohammad tagged the group of Commander Marahomsal Faisal and Nurham Amil alias Commander Ramzi the alleged leaders of a lost command of the Muslim separatist group Moro Islamic Liberation Front as responsible for the abduction of Pierantoni.
Atutubo said Mohammad has been turned over to the National Bureau of Investigation for further interrogation.
Abdusalam was apprehended in Barangay Tigbanwan in Tunguan town, Zamboanga del Sur a few hours after the kidnapping.
After his arrest, Abdusalam was made to escort a military team to their hideout in Margosatubig town where Pierantoni was being held.
While en route to the island aboard a pump boat, Abdusalam allegedly grabbed the rifle of one of the soldiers and fired indiscriminately, wounding two of the troops.
The soldiers fired back, killing Abdusalam and another suspected gangman, identified only as Hassan.
Atutubo said Abdusalam and Hassan fell overboard and were lost in the high seas.
Meanwhile, Atutubo said they have pinpointed the Pentagon hideout where Pierantoni is being kept. "We have already confirmed their location... our troops are there."
He said the joint rescue operation has focused on Malabang town in Lanao del Sur where the kidnappers and their hostage were reportedly sighted.
Atutubo said the gangmen had apparently transferred Pierantoni to Malabang following the capture of Abdusalam.
In another development, Lt. Gen. Roy Cimatu, commander of the Armed Forces Southern Command (Southcom) based in Zamboanga City, claimed that Faisal and Ramzi have aligned themselves with the Pentagon gang and demand an unspecified amount of ransom for Pierantoni.
The kidnappers have reportedly contacted Bishop Zacarias Jimenez of the Zamboanga prelature purportedly to relay their ransom demand.
Quoting intelligence reports, Cimatu said Pierantoni was being held in Barangay Tuka, Sultan Gumander town in Lanao del Sur.
Local officials in Lanao del Sur led by Rep. Benasing Macarambon have initiated negotiations for Pierantonis release, Cimatu said.
"There must be no ransom. We have to stick to the governments no-ransom policy," Cimatu stressed. With Paolo Romero