Defense Secretary Delfin Lorenzana confirmed on Thursday eight foreign nationals were among those killed in the offensive military operations in Marawi City.

The slain suspected foreign terrorists who were "ISIS (Islamic State of Iraq and Syria) members" are two Malaysians, two Indonesians, two Saudi nationals, a Yemeni and a Chechnyan, said Lorenzana in a press briefing in Malacanang, quoting Secretary Abul Khayr Alonto, chair of the Mindanao Development Authority (MinDA).

He said the eight foreigners were among the 33 identified slain suspected terrorists out of 120 killed.

Lorenzana said the foreign terrorists could have entered Mindanao through backdoor.

"We don't have any record of them coming from the proper channel, through the airports. There's only one way, through the backdoor, may be coming from Indonesia or from Malaysia, from Sabah," he said.

Lorenzana estimated there could be some 100 remaining Maute members, including Abu Sayyaf leader Isnilon Hapilon, the anointed leader of ISIS in the country, holed up in Marawi.

He admitted that the government forces find it hard penetrating the place where the Maute remnants were hiding because they were inside "fortified buildings" manned by snipers.

Based on intelligence report, he said Hapilon received "several million dollars worth of funds from the Middle East."

Because he has money, Hapilon, who is from the Yakan tribe, was able to buy the loyalties of some Maranao people in Marawi, he said.

"Culturally or whatever, these tribes do not mix. And there is only one reason there is that he has lot of money to distribute and buy loyalties," he said.

Initially, he said there were about 500 Maute militants who occupied Marawi.

While there could be around 100 who were still holed up in the fortified buildings, others could have left Marawi in small groups, Lorenzana said, citing information by civilians.

Asked if the Philippines would ask assistance from the United States in addressing the Marawi crisis, he said, "I don't think we need to ask because we already have a lot of equipment to contain this Marawi incident."

But he said the Philippines is still getting aid from the US through the operation of their drones, called birds.

"They have three birds...operating there and they're giving us intelligence information...I don't think they have some there in Marawi because it's too far away from Zamboanga where they operate shadows," he said.

"They are giving us (information) but I think very little for Marawi. But a lot from other areas like South China Sea, Sulu Sea, Sulu, Basilan, they are giving us lots of information. But here, just very minimal," he added. Celerina Monte/DMS