Sidney Jones, director of the Jakarta-based Institute for Policy Analysis of Conflict (IPAC), said on Saturday that Manila was apparently still in the dark over the identity of the bombing perpetrators.
"There's no evidence! Different officials are saying different things -- Malaysians, Yemenis, Indonesians. They actually have no clue," told Jones told The Jakarta Post via text message on Saturday.
Philippine Interior Minister Eduardo Manahan Año earlier said that based on witness accounts and information from undisclosed sources, he was convinced that Indonesian citizens committed suicide bombings at a Roman Catholic church in Jolo, the capital of Sulu province, which has long been plagued by separatism led by Islamist groups.
"They are Indonesians," Ano, a former military chief, told CNN Philippines, as reported by AFP. "I am certain that they are Indonesians."
He also claimed that other foreign terrorists were still operating in the Philippines, suggesting they could be either Yemeni or Egyptian.
Fitriani of the Centre for Strategic and International Studies (CSIS) concurred with Sidney, saying that without evidence it was too early to conclude that Indonesians were involved in the bombings.
However, she did not rule out the possibility of Indonesian militants being involved in the attacks given the geographical proximity between the two countries. Moreover, the border between Indonesia and the Philippines lies in the sea so it is hard to monitor.
During the armed conflict between the Maute group, which is linked to the Islamic State, and Philippine security forces in Marawi two years ago, a number of Indonesian militants were believed to have gone to the Philippine city to join the fight alongside the Maute militants.
At the time, calls for jihad in the Philippines circulated on social media accounts linked to Indonesian jihadi groups such as Jemaah Ansharu Daulah, which was said to have sent dozens of its members to the neighboring country.
Indonesia, Fitriani said, would have to share intelligence information with Manila and would even help with the investigation following allegations its citizens carried out a deadly terror act in a foreign country.
"Indonesia will usually share anything needed,” she said.
She argued that the bombings should serve as a wake-up call for Southeast Asian countries to strengthen their cooperation in the war on terror, particularly in terms of intelligence sharing. Indonesia has initiated intelligence partnership Our Eyes, which was endorsed by ASEAN member states last year.
"It is needed more than ever. Terrorism is an enemy to all countries," she said, adding that the Jolo attacks were feared to awaken sleeping terrorist cells in Indonesia and other neighboring countries.
Also on Saturday, Foreign Minister Retno LP Marsudi said she was still seeking confirmation regarding the identity of the bombing perpetrators.
She said Jakarta had talked to the Philippine authorities and was told that the identity of the perpetrators had not yet been determined.
"Based on information we gathered this morning, the perpetrators have yet to be confirmed because the investigation and identification process are still ongoing," said Retno in a video statement recorded in Padang, West Sumatra.
Retno further said that Jakarta had yet to decide what to do next as it was currently focusing on following the investigation process.