MARAWI CITY – Around 10 members of the Islamic State-linked Maute group have snuck into Marawi City to reinforce comrades battling state forces in the conflict zone, multiple sources told ABS-CBN News

The military neither confirmed nor denied the report but said government troops are ready for such possibility.

ABS-CBN News sources said that the Maute reinforcement took advantage of heavy rains to creep into the battle zone, entering Marawi via the Lanao Lake at nighttime, and landing in an area in adjacent Marantao town.

While ABS-CBN News was able to reach Marantao, residents refused to speak, and there were no police or military personnel in the area to confirm the reports.

"It is really possible to happen, kaya nga po naglagay tayo ng forces diyan sa area na iyan. Mayroon tayong Joint Task Group Lawa, composed of the PNP (Philippine National Police) and Special Forces, na nagco-conduct ng patrols, maritime patrols 24/7," said Capt. Jo-Ann Petinglay, spokesperson of Joint Task Force Marawi.

"If you can see, it's a 34 sqm na area. Napakalawak po ng lake. Isa po iyan sa ating mga challenges," she added.

This could mean prolonged operations in Marawi City, where clashes have continued for more than two months now. But Petinglay said ground forces have prepared for such a situation.

"Ang ating mga ground commanders are looking into all the possibilities na maaaring mangyari, including kung mayroon mang nakapasok," Petinglay said.

Coastal towns have started to implement security measures. In Balindong town, boat owners are required to register at the municipal hall. They should also paint numbers on their boats for easy identification.

The military is also confirming the authenticity of pictures of terror leader Omar Maute and Isnilon Hapilon of the Abu Sayyaf group, known to be the anointed ISIS leader in Southeast Asia.

One photo shows a wounded Omar Maute in a wooden house.

"Those pictures we have forwarded to our intelligence units for validation. Sa ngayon, hindi pa tayo nakatanggap ng kasagutan mula sa kanila. Isa rin iyan sa ating tinatanong—how come may mga pictures na ganito ngayon? Ano po ang mensahe, at ano po ang ibig sabihin?” Petinglay said.

President Rodrigo Duterte earlier offered a P10 million reward for the "neutralization" of Hapilon and P5 million each for brothers Abdullah and Omar Maute, leaders of the terror group under their name.

Task group commanders have prepared for the worst possible scenario, "with or without these leaders inside the main battle area," she added.

Other pictures gathered by ABS-CBN show Maute fighters killed by the military.

One fighter was found under the rubble. Another was killed in a business establishment, while the others were in vacant lots. Some of those slain were wearing military uniforms.

The military earlier said fighting in Marawi City was confined to an area less than 1 sqm, and that between 50 to 70 Maute terrorists remain in the conflict zone.

• READ: More intense firefights as Marawi siege nears end: Año

Since clashes erupted on May 23, 552 Maute fighters have been killed while 128 government troops have given up their lives.

The long-drawn crisis in Marawi, once a bustling commercial and cultural hub, has driven out more than 200,000 residents from the city and thousands more from nearby areas.