Four security guards were killed and two people were injured in a mass shooting at a popular fresh food market in Thailand's capital on Monday, police said.

"Police are investigating the motive. So far it's a mass shooting," Worapat Sukthai, deputy police chief of Bangkok's Bang Sue district where the incident took place, told AFP, adding that the gunman took his own life.

The shooting occurred at the Or Tor Kor market in Bangkok, according to Thai media reports. 

(With input from AFP)