MANILA, May 23 (Reuters) - Five Philippine soldiers were wounded on Tuesday in a clash when they raided an apartment where Islamic State-linked militants were hiding in a city on the southern island of Mindanao, the army said.

The focus of the raid was about 15 militants belonging to the Maute group, which has pledged allegiance to Islamic State in the Middle East. The fighting was still going on by nightfall.

Lieutenant Colonel Jo-ar Herrera, an army spokesman, said the military was acting on information that Isnilon Hapilon, a leader of the Abu Sayyaf rebel group, was among the militants hiding in the apartment in Marawi City.

The U.S. State Department has a bounty of up to $5 million for his arrest.

The Maute and Abu Sayyaf have an alliance and are both linked with Islamic State, a source of growing concern for President Rodrigo Duterte, who has warned of the expanding influence of the militants in the Philippines.

Some residents fled Marawi when the fighting erupted and soldiers blocked off roads. Officials urged residents to avoid spreading rumours that rebels has seized a hospital.

Security forces in the mostly Christian Philippines have battled Muslim separatists for decades and peace efforts have led to a reduction in clashes with main groups.

However, small, violent factions, some with a more radical agenda, have broken away from main groups and stepped up attacks.

Government troops have been intensifying offensives on the island strongholds of Abu Sayyaf and last month killed about 36 Maute group fighters when aircraft bombed their mountain lair in Lanao del Sur province.

(Reporting by Manuel Mogato; Editing by Martin Petty, Robert Birsel) ((manuel.mogato@thomsonreuters.com; +63 28418913;))