Bangkok: Thirty-six people have died after a gunman burst into a popular hotel casino in Manila early on Friday morning, firing shots, setting gaming tables alight and sparking panic.

Most of the victims are believed to have died from suffocation.

At least 54 people were injured as they stampeded from the Resorts World Manila building in the Philippine capital after the attack by a "tall foreign-looking" gunman with a moustache, police said.

The man's burnt body was also found in a guest bedroom in the complex. 

The gunman shot himself and then doused himself with a liquid and set himself alight.

The incident came in the country on high alert after martial law was declared in the south. However, Presidential spokesman Ernesto Abella said the incident was not linked to Islamist militants occupying a city in the southern Philippines.

"All indications point to a criminal act by an apparently emotionally disturbed individual. Although the perpetrator gave warning shots, there apparently was not indication that he wanted to do harm or shoot anyone. The 34 deceased all died to suffocation," Abella told a media briefing.

Police later updated the death toll to 36.

Oscar Albayalde, chief of the Manila police office, said the gunman died after setting himself on fire. He was burnt beyond recognition, police said. 

Earlier, police said they had killed the gunman, amid reports that he had been shot dead. 

Johnny Ordanza, an employee of the hotel, said he saw at least one person started to set tables on fire on the second floor of the casino and firing shots.

"There were other gunmen because we can hear gunshots elsewhere," he told Manila radio station DZMM.

"They were not targeting the casino players, and we rushed out through the emergency exits." Police later said they believed the gunman was acting alone.

Witnesses said that after the gunman set the gaming tables alight, he left the gambling area and went upstairs to a hotel section of the complex, prompting police to search the hotel room by room.

The gunman also forced his way into a storage room and grabbed gambling chips, which he put in his backpack.

But amid the chaos he left the backpack behind, which forensic experts were examining.

Some of the wounded were injured jumping from the hotel's second-floor balconies to escape the gunman, Fernando Atienza, a Red Cross spokesman, told the Manila Times.

Resorts World Manila is the largest casino resort in the country, according to its website, and is located across the road from Terminal Three of Ninoy Aquino International Airport. All flights from Manila's international and domestic airports were grounded following the incident.

Tight security has surrounded a just completed 57-storey Trump Tower at Century City in Manila's financial district of Makati. The US$150 million building is licensed under the Trump brand.

Australia warned early Friday morning that the deterioration of security in Mindanao "has resulted in a more volatile security environment in the Philippines".

"Travellers are reminded of the high threat of terrorist attack in the Philippines, even Manila," the Department of Foreign Affairs said in an updated post on its smartraveller.gov.au website.

The post advised people to stay away from Resorts World Manila.

Security forces in Manila have been on high alert during a nine-day siege of the southern Philippine city of Marawi by extremists linked to IS.

Check-points have ringed sprawling Manila amid fears that militants would target the capital in retaliation the fierce fighting in Marawi, 830 kilometres south of Manila, where dozens of fighters from the Maute group have been killed. Military air and group strikes have failed clear the city of 200,000.

Analysts say militants seized Marawi as part of a coordinated plan for a dozen groups to gain a foothold in the southern Philippines. The groups, including the brutal Abu Sayyaf, have sworn allegiance to IS.

The Abu Sayyaf has in the past carried out bombings, kidnappings and assassinations across the Philippine islands that have killed hundreds of people.

Philippine security forces last week botched an operation in Marawi to capture Isnilon Hapilon, the Abu Sayyaf's leader and the head of IS in the Philippines.

He escaped but according to some reports may be injured.

Washington has a US$5 million bounty of Hapilon's head.

President Rodrigo Duterte is now expected to declare martial law across the whole of his country after the Resorts World Manila attack.