The Phillipines' president has offered $410,000 for the "neutralisation" of Isnilon Hapilon, Abdullah Maute and his brother Omarkhayam Maute. The three are said to be the leaders of the militants fighting troops in Marawi.
Philippine President Rodrigo Duterte offered large bounties on Monday for the leaders of militant groups holding parts of a southern city as the military warned its recapture may take longer than expected.
Hundreds of gunmen loyal to Daesh are battling air strikes, artillery and ground forces in Marawi. Up to 2,000 civilians are believed to have been trapped for two weeks in districts held by the militants, the government says.
The fighting has killed at least 178 people and caused nearly a quarter of a million others to flee, according to government officials.
Fresh rewards totaling 20 million pesos ($410,000) are on offer from Duterte for the "neutralisation" of Isnilon Hapilon, Abdullah Maute and his brother Omarkhayam Maute, a military statement said.
"We hope that this will bear significant accomplishments leading to the eventual arrest and neutralisation of Isnilon Hapilon and the Maute brothers," military chief of staff General Eduardo Ano said in the statement.
Top leader of Daesh
Half the amount will be for Hapilon, whom Ano described as the "amir" or top leader of Daesh in the Philippines.
The US government also has a $5 million bounty on Hapilon's head for the kidnapping and killing of US citizens, as well as a standing bounty of 7.4 million pesos ($150,000) by the Philippine government.
Manila says it is fighting up to 250 gunmen holed up in central Marawi, the largely Catholic nation's most important Islamic city and home to 200,000 people.
The gunmen are a combination of Hapilon's Abu Sayyaf group, blamed for the country's deadliest bombings as well as kidnappings, and militants led by the Mautes, based in the Marawi region.
More than 224,000 residents of the city and nearby towns have fled the fighting, the provincial government said Monday.
Shortly after the violence erupted Duterte imposed martial law across the southern region of Mindanao, home to 20 million people, to quell what he said was a bid by Daesh to establish a base in the country.
Defeat proving difficult
The military warned on Monday that defeating the militants, who are also believed to include several foreign fighters, was proving "difficult" even though 120 of them had been killed.
The gunmen were using an extensive network of tunnels and basements built many years ago beneath the buildings they have seized, military spokesman Lieutenant-Colonel Jo-ar Herrera said.
They had also cited powerful weapons such as machine guns inside mosques and traditional Islamic schools that are off-limits to air strikes and artillery attacks, he added.
"What they are doing is un-Islamic," he said.
The buildings are also believed to contain at least a month's worth of food stocked up by their owners for the entire Muslim fasting month of Ramadan that coincided with the fighting, Herrera added.