A police major was among four people shot dead at a gambling den in Yannawa district overnight, reportedly by a losing gambler. Police were hunting for the killer.

According to media reports, the shooting occurred after a man of Chinese appearance drew a gun, claimed  he was being cheated and demanded his money back. 

The city police chief said on Tuesday the slain officer was not on duty. He was there for the gambling.

The den was operating on the ground floor of a four-storey commercial building surrounded by security cameras about 300 metres off Rama III Road in soi 66.

The premises had strong doors and access appeared heavily restricted. There were chairs and tables, and monitor screens on the walls.

Reports said several gunshots were fired about 10 o'clock on Monday night. Four people were killed - the police officer, another man and two women.

Bangkok police chief Pol Lt Gen Pakapong Pongpetra rushed to inspect the scene, and left it without answering reporters' questions.