Passers-by treat injured pedestrians and motorists after they were hit by a gunman during a mass shooting in Thailand today.

The killer - Sergeant Major Jakrapanth Thomma - killed three at an army camp then opened fire at the Terminal 21 building in the city of Korat, Nakhon Ratchasima province, shortly before 6pm.

Dozens of bodies littered the roads outside the building, with injured people being treated by passers-by.

The gunman shot a gas tank causing an explosion and fire then killed shoppers, pedestrians and motorists with a rifle and machine gun. The shooter then walked into the mall and took people hostage while hundreds fled outside or hid in dark rooms.

Horrifying footage from onlookers shows the masks shooter - who is still ACTIVE - picking people off with a rifle. At least two police officers have been killed. Many more are believed to be injured after the shooting spree, during the busiest time of the week.

Pictures show the bloodbath with bodies littered across the roads near the shopping centre and slumped in their cars.

Police and military have raced to the scene while the monitor CCTV from inside the building. At least one officer armed with a semi-automatic handgun has entered the building in search of the killer.

Colonel Kritsana Pattanacharoen said the military knew about the shooter identity and insisted people to stay away from the scene.

Major General Apirat Kongsompong said he had ordered all available police and military units in the area to attend the scene.