A lone gunman entered the Resorts World Manila early Friday, firing shots from an assault rifle and setting fire to gambling tables. Most of the victims are believed to have died due to suffocation from the smoke.
ISIS claimed that "Islamic State fighters carried out" the attack in a statement Friday by its Amaq News Agency. A follow-up statement from the group's east Asia division referred to only one attacker -- whom it named as Abou al-Kheir al-Arkhebieli -- and boasted about the number of "Christians killed or wounded" before he "took his life."
But police said there was "no truth" to the assertion.
"They can always claim whatever they want to claim," said Oscar Albayalde, police chief for the Manila area. "They have this reputation of claiming all atrocities all over the world to perpetuate themselves to gain global notoriety. There is no truth that the incident is a terror act."
The sequencing of ISIS' claims is not unusual. But CNN terrorism analyst Paul Cruickshank pointed out that the first claim of responsibility referred to multiple attackers, while the second mentioned only one.
"Until any actual proof emerges that ISIS or any other terrorist actor had a role in what police have described as a non-terrorism-related attack, one has to be skeptical of the ISIS claim," Cruickshank said, adding that Abou al-Kheir al-Arkhebieli would likely be a nom de guerre.
Philippine government forces have been battling ISIS-linked militants on the southern island of Mindanao
for control of the city of Marawi for more than a week.
How the attack unfolded
Around midnight Thursday, an armed suspect forced his way into the Resorts World Manila, an upmarket hotel and casino complex near the Ninoy Aquino International Airport.
According to security footage viewed by police, the gunman entered via the parking lot. Police later searched a car and found registration information they haven't made public.
The attacker walked into the building and past a lone security guard, who panicked when she saw the suspect's automatic rifle, said Albayalde, the Manila police official.
Stephen Reilly, the resort's chief operating officer, said only guards on the complex's perimeter are armed. Internal security officers, who don't carry weapons, didn't try to engage the suspect, fearing escalation of the situation, he said.
Video showed guests frantically running for the exits, the sound of gunshots and smoke coming from the upper floors of buildings.
The man ransacked a room and stole gaming chips, Philippine National Police Chief Ronald Dela Rosa said. He stuffed chips totaling 113 million pesos ($2.3 million) in a backpack, which police later recovered, he said.
During the attack, the gunman engaged in a firefight with casino employees, police said.
The attacker was shot and wounded by security guards, and retreated into a hotel room, where he doused a bed with gasoline and shot himself, according to Reilly.
The attacker was found dead around 7 a.m. local time, according to a statement from the resort
CNN Philippines reported
he was found in the room, burned beyond recognition, next to an automatic weapon and a .380-caliber pistol.
Witness 'could smell smoke'
Hundreds of guests and employees rushed out of the resort after the gunman began shooting on the second floor, hotel employees fleeing the scene told CNN Philippines.
Jay Dones, a witness, said some employees had told him a gunman fired shots in the air.
"One of the employees told me that the suspect began pouring the contents of (a) bottle on one of the tables and lit it on fire," Dones said.
Witnesses also spoke of hearing what sounded like explosions.
"I could smell some kind of smoke that came from an explosive device," said Tikos Low, who said he was in the resort's casino when the attack began.
Of the 37 victims, management said 13 were employees of the casino while the rest were guests. Police haven't identified the bodies of six people, including two employees and four guests.