The national police chief said the gunman apparently barged into a room at the 5th floor of the Maxims hotel connected to the mall and casino, laid on the bed, blanketed himself, doused himself with gasoline then set himself on fire.
The armed suspect forced his way into the Resorts World Manila (RWM), an upmarket hotel and casino complex near the Ninoy Aquino International Airport, around midnight local time (Thursday ET).
"They can always claim whatever they want to claim", said Philippine national police chief Oscar Albayalde.
The gunman did not appear to be firing at people, said Dela Rosa, which suggested the incident was not terror-related.
Manila police believe the attacker is a foreigner, telling reporters, "He looks Caucasian, he talks English, he's big and he's White".
He was carrying a rifle and had shot at TV screens, set tables on fire and stuffed a bag with gambling chips.
The man then left the room and went upstairs to a hotel section of the complex, according to dela Rosa.
"The market is taking it as it has been described in the news, that it is more of a criminal event rather than a terrorist event which just happened to coincide with what's happening in Mindanao", said Alan Cayetano, head of foreign currency trading at Bank of the Philippine Islands. Resorts World security and police pursue the gunman who is able to climb to higher hotel floors.
Rejecting the claim, police said there was "no truth" to the assertion.
The unidentified suspect died after setting himself on fire, authorities said.
At least 35 people died at Resorts World Manila in the Philippines after a gunman stormed the resort in an attempted robbery and torched gambling tables, creating a choking amount of smoke, law enforcement and company officials said. "He only went for the casino chips".
The Metropolitan Manila police chief previously said 36 bodies were found inside the building by firefighters and all died from smoke inhalation.
Ho declined to say how he would increase security but said his casinos already make use of surveillance and counter intelligence measures, metal detectors and security guards.
A statement from the ISIS-affiliated Amaq News Agency said "Islamic State fighters" carried out the attack.
Officials said at least 54 people were hurt as they rushed to escape what at first had been feared as a militant attack.
Police said after the theft, the suspect was shot and wounded by security guards. Chips totaling $2.3 million were found in a backpack recovered by police, he added.
"I was about to return to the second floor from my break when I saw people running". US President Donald Trump also branded it a "terrorist attack". Trump said he was "closely monitoring the situation" and would continue to provide updates.