The marines were doing a house-to-house search for militants aligned with the Daesh terror group who are still possessing many parts of Marawi City when the battle erupted Friday, said Lt. Col. Jo-ar Herrera, representative for the Philippine armed force's first Infantry Division.
The militants seized Marawi on May 13 and are still occupying parts of the city.
Forty other marines were wounded.
At least 138 militants and 20 civilians have also been killed, the government says.
"The local terrorist groups are using the mosque; they are entrenched there". In 2002, the United States helped Philippine authorities track down Abu Sayyaf leader Abu Sabaya, who was killed in that operation.
Thousands of Marawi's 200,000 inhabitants fled the city after Islamic State-linked militants executed civilians, while the nation battled a deadly casino attack last week labelled as a 'terrorist' act by a top Philippine lawmaker. "American forces have always been present - although they are there primarily for technical and intelligence support".
"They are not fighting".
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About 40 foreigners have fought alongside the Philippine militants in Marawi City, majority from Indonesia and Malaysia, though some came from the Middle East.
Marine Commandant Maj Gen Emmanuel Salamat confirmed the casualties to GMA News website on Saturday (June 10), saying that government troops and militants from the Maute group had been involved in a 16-hour clash in Barangay Lilod Madaya that began at around 3.30am on Friday.
The BBC's Jonathan Head says there are several reports that the Maute brothers, who lead the Maute group, are among the dead, with intercepted communications from jihadist groups suggesting this.
The military on Saturday said that this is the biggest single-day loss for the government forces in a battle which has been ongoing for almost three weeks.
Gen. Restituto Padilla said told AP by phone, citing a Philippine government policy that bars foreign troops from participating in local combat.
An Associated Press journalist and photographer saw a U.S. Navy P3 Orion plane hovering in cloudy skies above Marawi on Friday.
Philippine military leaders have said their troops unexpectedly interrupted plans by the fighters to take over Marawi in a spectacular event to show that IS had arrived in the Philippines and was intent on carving out territory.