The gunman killed himself by setting himself on fire. Police said the incident appeared to have been a robbery attempt, and was not terror-related. Authorities said most of the dead appear to have suffocated from thick smoke after the man set fire to casino tables. 
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. 
President Rodrigo 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.