So far, authorities say that one gunman, described as Caucasian and foreign, was behind the attack.
Metropolitan Manila police chief Oscar Albayalde said the 36 bodies were found in the smoky gambling room by firefighters and all died from suffocation and smoke inhalation. "Before we exited, we heard two gunshots and there was thick smoke on the ground floor", Navaro said.
At the Palace briefing, Presidential Spokesman Ernesto Abella reiterated the position taken by authorities that the incident was not related to the ongoing clashes between local terrorist groups and government forces in Marawi City.
He said the gunman parked his auto at the second floor of the building, started firing in the air and burned some tables before entering the storage room.
Stephen Reilly, the resort's Chief Operating Officer, said the attacker was shot and wounded by security guards, and retreated into the hotel room where he doused a bed he was lying on in gasoline and shot himself.
Officials said they recovered the suspect's bag, which was filled with casino chips.
Albayalde said at the news briefing around noon that the police had some doubts on robbery as a possible motive for the attack.
It was not immediately clear how many people may have been injured or killed.
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"If he were a terrorist, he would have strapped a bomb or TNT onto himself and detonated himself to inflict more damage", Albayalde said.More news: Bihar: Failed students continue protests
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A maintenance worker from the casino told the same station that he saw a woman fall from an upper floor while trying to escape. "I could not carry her".
It is really sad with what's going on throughout the world with terror. He said he was "closely monitoring the situation" and would continue to provide updates.
An earlier SITE report quoted an "IS operative" confirming the group's role in the attack on the encrypted messaging app Telegram.
The unrest in Marawi had sparked fears that militants might attack elsewhere to divert the focus of thousands of troops deployed to the city. While U.S. President Donald Trump said publicly that the violence had "terror" links, Dela Rosa said there was no solid evidence linking the case to terrorism.
Information for this article was contributed by Teresa Cerojano, Joeal Calupitan and Bullit Marquez of The Associated Press.
Gunshots and explosions rang out early Friday at a mall, casino and hotel complex near Manila's global airport in the Philippine capital, sparking a security alarm amid an ongoing Muslim militant siege in the country's south.
On the stock market, shares of Philippine casino operators fell sharply as trading opened in Manila on Friday.
Hundreds of guests and employees rushed out of the resort hotel as soon as the gunman began shooting, CNN reported.
Policemen walk past a still smoldering part of a hotel at the Resorts World Manila complex, early Friday, June 2, 2017, in Manila, Philippines. CCTV footage provided to media by police show the gunman, wearing a black bonnet and carrying a baby armalite, in one of the stairwells in the casino complex.