Police say victims died from suffocation and smoke inhalation after attacker raided resort and then killed himself.

More than 30 people have died after a gunman burst into a casino in Manila, capital of the Philippines, firing shots and setting gaming tables alight, according to officials.

The attack took place shortly after midnight (16:00 GMT) at the Resorts World Manila complex, police said on Friday, adding that all the victims died from suffocation and smoke inhalation.

“Thirty-six deaths, this is due to suffocation,” Manila police chief Oscar Albayalde told CNN Philippines.

Police had previously said that at least 25 people died in what they described as a botched robbery attempt.

The unidentified gunman self-immolated after firing at armed officers and causing havoc in the casino, according to police.

“He laid down on the bed, covered himself in a thick blanket and apparently doused himself in gasoline,” Ronald dela Rosa, national police chief, told reporters, adding that a sub-machine gun and a small calibre gun were captured with the attacker.

READ MORE: Resorts World Manila complex on lockdown after attack

The gunman stole gambling chips, shot TV screens and set gambling tables ablaze after pouring gasoline on them, dela Rosa said.

Claims on social media said the attack was executed by “lone wolf soldiers” of the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group, but police noted the man did not shoot anyone he encountered.

“He would have shot all the people gambling there” if it had been “terrorism”, dela Rosa added.

It was not clear how the gunman smuggled gasoline and an assault rifle into the crowded casino.

Ernesto Abella, a spokesman for President Rodrigo Duterte, echoed the police statements at a press conference later.

“All indications point to a criminal act by an apparently emotionally disturbed individual,” Abella said.

“Although the perpetrator gave warning shots, there apparently was no indication that he wanted to do harm or shoot anyone.”

Police: ‘Attacker probably a foreigner’

Albayalde, the Manila police chief, said the attacker was likely to be a foreigner.

“He looks Caucasian, he talks English, he’s big and he’s white, so he’s probably a foreigner,” Albayalde said. “It’s either he lost in the casino and wanted to recoup his losses or he went totally nuts.”

The entertainment complex where the incident happened is close to Ninoy Aquino International Airport and an air force base.

The Philippines has been on heightened alert amid a crisis in the south of the country, where troops have been battling ISIL-linked rebels since May 23 in Marawi City, some 800km south of Manila.

President Duterte declared martial law on the southern island of Mindanao last week and warned it could become a haven for supporters fleeing Iraq and Syria.

Dela Rosa, the national police chief, said there was no credible “terror” threat in Manila so far.