MANILA/MARAWI, Philippines (Reuters) - The Philippine Supreme Court on Tuesday upheld as constitutional President Rodrigo Duterte’s imposition of 60 days of military rule on a southern island, a ruling that would reinforce unity in the fight against militancy, his spokesman said.

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Duterte placed the southern island of Mindanao under military rule on May 23, hours after hundreds of pro-Islamic State militants seized control of the predominantly Muslim town of Marawi, which is on the island.

Eleven members of the 15-member court bench ruled the president’s order valid. Three agreed with it but wanted to limit the area of martial law and one judge opposed it, said court spokesman Theodore Te. He did not elaborate.

Six weeks after the imposition of martial law on the island, government forces are still battling the rebels in the town.

Hundreds of people have been killed and alarm has spread across the region about the prospects of Islamic State establishing a Southeast Asian foothold in the troubled south of the predominately Christian Philippines.

“With the Supreme Court decision, the whole government now stands together as one against a common enemy,” presidential spokesman Ernesto Abella said in a statement.

Defense Secretary Delfin Lorenzana said he was hopeful the battle with the militants of the previously little-known Maute group would be over before the 60-day period of martial law ends, as the Philippines’ was getting more help from allies.

Two Australian P-3C Orion surveillance planes, manned by joint Australian and Philippine crews, have started flying over Marawi, to pinpoint the locations of the militants, Lorenzana said.

The aircraft will be in the Philippines for two weeks.

On Tuesday morning, clouds of smoke hung over the lakeside town as troops fired on militant positions with artillery and machine guns from helicopters.

Sporadic explosions were heard later in the day.

The army said it had captured another militant stronghold, a century-old college set up by Americans which the rebel leaders, brothers from the Maute family, had attended.

An army spokesman, Lieutenant-Colonel Jo-Ar Herrera, said troops had also recovered the body of a militant who was believed to be from Singapore, bringing to 11 the number of foreign fighters killed in the battle.

It was not clear why authorities believed the fighter was from Singapore. Herrera only said they had information.

More than 400 people, including 337 militants and 85 members of the security forces, have been killed in the fighting in Marawi. Forty-four civilians had also been killed, either in crossfire or executed by the militants, the military said.