Footage from the hospital in Nakhon Ratchasima, northern Thailand, where survivors of a mass shooting were being treated overnight.

More than 20 injured people were taken to the hospital after gunman Sergeant Major Jakrapanth Thomma, killed at least 20 people and injured 40 others during a rampage shortly before 6pm local time on Saturday (February 8).

Three seriously injured victims were flown by helicopter to Bangkok for emergency treatment.

The country's Public Health Minister Anutin Charnvirakul is seen in green top visiting the medics and patients. Other locals flocked to the hospital to donate blood to treat the victims.

Meanwhile, armed police are surround the Terminal 21 shopping mall where the shooter has taken hostages.