Thai officials say a soldier who went on a shooting rampage and killed at least 26 people and injured 57 others has been shot dead inside a mall in north-eastern Thailand.

Officials said the soldier, angry over a financial dispute, first killed two people and then went on a far bloodier rampage, shooting as he drove to a busy mall where shoppers fled in terror.

Defence Ministry spokesman Lieutenant General Kongcheep Tantrawanich said Sergeant Major Jakrapanth Thomma was behind the attack in Nakhon Ratchasima, a hub for Thailand’s relatively poorer and rural north-eastern region.

Much of the shooting took place at Terminal 21 Korat, an airport-themed mall filled with colourful Lego sculptures, a merry-go-round and huge replicas of landmarks from around the world.

Video taken outside the mall showed people diving for cover as shots rang out mid-afternoon Saturday.

Many were killed outside the mall, some in cars, others while walking.

"Hanuman" police commandos arrive in Korat city after a 40-minute helicopter ride from Bangkok to assist in an operation to kill or capture a gunman who murdered at least 12 people in a shooting rampage. #กราดยิงโคราช #Thailand https://t.co/1qWp0y3VQy pic.twitter.com/LZKaa0OMEI

— Khaosod English (@KhaosodEnglish) February 8, 2020

Jakrapanth was a sharpshooter and took many special courses on attacking, including planning ambushes, army sources said, and Thai media reported he often posted photos of weapons on social media.

The soldier drove to the mall in a stolen Humvee and was armed with an assault weapon and ammunition stolen from the army base’s arsenal, an official said.

He initially posted written messages on Facebook during the attack before his account was shut down by the company.

“It was a personal conflict … over a house deal,” Prime Minister Prayuth Chan-ocha told reporters on Sunday from Nakhon Ratchasima after travelling there to meet wounded survivors.

Mr Prayuth added that the conflict was with a relative of the soldier’s commanding officer.

Hundreds of shoppers fled the mall in groups crouching low, and the police and army launched several rescues during the more than 12-hour stand-off, with armed forces at one point emerging at a run carrying small children.

“It was frightening because I could hear the occasional gunshot … we waited a long time for the police to come and help us, many hours,” said Suvanarat Jirattanasakul, 27, her voice trembling after she emerged.

Another survivor identified as “Diaw” told local Amarin TV that the shooter was “aiming for the heads” and said his colleague died on the scene.

CCTV footage from inside the mall posted on social media showed the gunman dressed in black and wearing a mask, his gun slung over his shoulder with no sign of other people around.

The shooter reportedly worked at an army base close to Nakhon Ratchasima, which is about 250 kilometres from the capital Bangkok.

Nattaya Nganiem and her family had just finished eating and were driving away when she heard gunfire.

“First I saw a woman run out from the mall hysterically,” said Nattaya, who shot video of the scene on her phone. “Then a motorcycle rider in front of her just ran and left his motorcycle there.”

Hundreds of people were evacuated from the mall in small batches by police while they searched for the gunman.

“We were scared and ran to hide in toilets,” said Sumana Jeerawattanasuk, one of those rescued by police. She said seven or eight people hid in the same room as her.

“I am so glad. I was so scared of getting hurt,” she said.

Shortly before midnight, police announced they had secured the above-ground portion of the mall, but were still searching for the shooter.

About 16 hours later, officials held a news conference outside the mall to announce the gunman was fatally shot. The officials did not release any details.

Lt Kongcheep told Thai media that the first person killed was the commanding officer of the 22nd Ammunition Battalion, in which the suspect also served.

A Thai soldier with a rifle caught on security footage at the Terminal 21 shopping centre.

City and neighbourhood police officers, who asked not to be identified because they were not authorised to release information, said the man fired shots as he drove to the mall.

Thai Rath television aired mall security camera footage showing a man with what appeared to be an assault rifle.

The man also posted updates to his Facebook page during the rampage.

“No one can escape death,” read one post.

Another asked, “Should I give up?”

In a later post, he wrote, “I have stopped already.”

A photo circulated on social media that appeared to be taken from the Facebook page shows a man wearing a green camouflaged military helmet while a fireball and black smoke rage behind him.

Jakrapanth’s profile picture shows him in a mask and dressed in military-style fatigues and armed with a pistol.

The background image is of a handgun and bullets. The Facebook page was made inaccessible after the shooting began.

A Facebook photo of the suspected killer who shot dead his commanding officer.

Many malls in Thailand, including Terminal 21’s namesake in Bangkok, have metal detectors and security cameras at entrances manned by uniformed but unarmed security guards.

Checks on those entering are often cursory at best.

Thai rescue workers tend to victims of a soldier who “went mad” and killed 20 people. Photo: AAP

Gun violence is not unheard of in Thailand.

Firearms can be obtained legally, and many Thais own guns. Mass shootings are rare, though there are occasional gun battles in the far south of the country, where authorities have for years battled a long-running Islamic separatist insurgency.

-with AAP