At least 36 people are dead and 54 injured in the Philippine capital of Manila after a lone gunman burst into a casino and opened fire.

Despite US President Donald Trump describing the incident at Resorts World Manila entertainment complex as a 'terrorist' attack, local officials say they believe it to be a botched robbery attempt and not linked to terrorism.

'All indications point to a criminal act by an apparently emotionally disturbed individual,' a spokesman for President Rodrigo Duterte said. 'Although the perpetrator gave warning shots, there apparently was no indication that he wanted to do harm or shoot anyone.'

There was no evidence linking the attack to fighting between government troops and Islamist militants in the country's south, he added.

Most of the dead suffocated in the chaos as guests and staff tried to flee choking smoke at the complex after the drama that began shortly after midnight (1700 BST).

Oscar Albayalde, chief of the capital's police office, said those that died were in the casino's main gaming area.

'What caused their deaths is the thick smoke,' he told reporters. 'The room was carpeted and of course the tables, highly combustible.'

A Resorts World Manila official said the dead included 13 employees and 22 guests.

Around dawn, the body of the suspected gunman was found in a hotel room in the still-smoking complex, which is close to Ninoy Aquino International Airport and an air force base, police said.

'He burned himself inside the hotel room 510,' national police chief Ronald dela Rosa told a media conference. 'He lay down on the bed, covered himself in a thick blanket and apparently doused himself in gasoline.'

Resort owner Travellers International Hotel Group Inc, a joint venture of the Philippines' Alliance Global Group Inc and Genting Hong Kong Ltd, said authorities were still seeking details.

'We have been informed of several casualties, the number and identities of whom have yet to be determined,' a statement read. Its shares were down 7 percent.

National police chief dela Rosa told the public: 'Don't panic, this is not a cause for alarm. We cannot attribute this to terrorism.'

'We are looking into a robbery angle because he did not hurt any people and went straight to the casino chips storage room. He parked at the second floor and barged into the casino, shooting large TV screens and poured gasoline on a table setting it on fire,'  he said.

Police said the gunman was tall with a pale complexion and spoke English.

Kimberly Molitas, a spokeswoman for the capital's police office, said 113 million Philippine pesos (1.77 million pounds) worth of casino chips stolen during the raid had been recovered.

Videos posted earlier on social media showed people fleeing as several loud bangs were heard.

The Philippines has been on heightened alert amid a crisis in the south of the country, where troops have been battling Islamist rebels since May 23.

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

Additional reporting from Reuters.