A police officer who witnessed the aftermath of a shootout between rival biker gangs in Texas has described it as “one of the most gruesome crime scenes” he has seen in more than three decades.

Sergeant W. Patrick Swanton said the Twin Peaks restaurant was littered with dead bodies, bullet casings, knives, weapons, shattered glass and pools of blood on Sunday night.

At least nine people were killed when fighting broke out between up to 200 bikers who gathered for a meeting in the city of Waco.

Almost 200 suspects have been detained and 18 people were injured in the brawl that sent families fleeing from the suburban shopping centre.

Restaurant staff reportedly hid in a back-room freezer as bikers were shot, stabbed, clubbed and beat each other with chains.

The violence erupted at around noon local time after an argument reportedly started in a toilet and spilled out into the restaurant and then its car park.

Deadly shootout between biker gangs Show all 18 1 /18 Deadly shootout between biker gangs Deadly shootout between biker gangs Waco shootout A McLennan County deputy stands guard near a group of bikers in the parking lot of a Twin Peaks restaurant in Waco, Texas. AP Deadly shootout between biker gangs Waco shootout Police detain and watch members of various motorcycle clubs outside the Twin Peaks restaurant in Waco, Texas. AP Deadly shootout between biker gangs Waco shootout A law enforcement officer walks past debris near the parking lot of a Twin Peaks restaurant on Sunday. AP Deadly shootout between biker gangs Waco shootout Authorities investigate a scene near a Twin Peaks restaurant on Sunday, 17 May in Waco. AP Deadly shootout between biker gangs Waco shootout Emergency responders tend to a wounded person near a Twin Peaks restaurant. AP Deadly shootout between biker gangs Waco shootout Bikers wait in a line as law enforcement officers investigate the parking lot. AP Deadly shootout between biker gangs Waco shootout Bikers congregate against a wall while authorities investigate a Twin Peaks restaurant. AP Deadly shootout between biker gangs Waco shootout A look at the motorcycles parked outside the Twin Peaks bar and restaurant, the scene of a multiple-fatality shooting between rival biker gangs. EPA Deadly shootout between biker gangs Waco shootout Law enforcement officers talk to a man near the parking lot of a Twin Peaks Restaurant on Sunday. AP Deadly shootout between biker gangs Waco shootout Bikers wait on a hill near the parking lot of a Twin Peaks restaurant on Sunday. AP Deadly shootout between biker gangs Waco shootout Authorities block an access road as an investigation continues near a Twin Peaks restaurant on Sunday. AP Deadly shootout between biker gangs Waco shootout Authorities investigate a shooting in the parking lot of the Twin Peaks restaurant. AP Deadly shootout between biker gangs Waco shootout People at the Central Texas MarketPlace watch a crime scene near the parking lot of a Twin Peaks restaurant AP Deadly shootout between biker gangs Waco shootout Customers leave the restaurant after the shooting AP Deadly shootout between biker gangs Waco shootout The Cossacks biker gang were one of the groups gathered at the meeting AP Deadly shootout between biker gangs Waco shootout Rival biker gangs had gathered for a meeting AP Deadly shootout between biker gangs Waco shootout Bikers wait in a line as law enforcement officers investigate the parking lot Rod Aydelotte/Waco Tribune-Herald via AP Deadly shootout between biker gangs Waco shootout AP

A spokesperson for the Waco Police Department said that the nine people killed were all members of the Bandidos and Cossacks biker gangs, believed to be rivals in the local area.

They were among at least five groups gathered for a pre-arranged meeting of Texas motorcycle clubs.

Police had been alerted in advance and were stationed outside in marked patrol cars but their presence did not prevent gunmen opening fire in public.

Sgt Swanton claimed that officers shot at armed bikers to prevent further deaths but it was unclear who had shot the men who died.

“This is probably one of the most gruesome crime scenes I've ever seen in my 34 years of law enforcement,” he added.

“I was amazed that we didn't have innocent civilians killed or injured.”

Even as police were shutting down the area, making arrests and seizing weapons, more armed men were arriving at the scene.

The Waco Police Department posted repeated warnings on Facebook urging curious members of the public to stay away from the shopping centre while they dealt with the “very dangerous individuals”. “This is not the time to sight-see,” the message added.

Sgt Swanton said the meeting focused on turf and recruitment, two areas where the groups had often clashed, but bikers claimed the event was a meeting of the non-criminal Texas Confederation of Clubs and Independents.

Doug Greeness, a biker who said he was a member of a family riding club, said the group met to “discuss issues within the biker community”.

Authorities investigate a scene near a Twin Peaks restaurant in Waco, Texas. (AP)

Managers at the Twin Peaks restaurant were also aware of the event in advance and police criticised them for not doing more to stop such large numbers of bikers gathering there.

The chain restaurant brands itself as having “scenic views” and is known for its scantily clad waitresses with “girl next door charisma and playful personalities”, according to its website.

A spokesperson for the Twin Peaks head office in Dallas said the Waco restaurant’s licence could be revoked as the company was “very upset” that safety standards had not been upheld.

The Twin Peaks restaurant chain is known for its scantily clad waitresses

Jay Patel, operating partner at the restaurant where the shooting took place, said he was “horrified by the criminal, violent acts”.

“We share in the community's trauma,” he said in a statement.

“Our priority is to provide a safe and enjoyable environment for our customers and employees, and we consider the police our partners in doing so.

Emergency responders tend to a wounded person near a Twin Peaks restaurant. (AP)

“Our management team has had ongoing and positive communications with the police and we will continue to work with them as we all want to keep violent crime out of our businesses and community. We will continue to cooperate with the police as they investigate this terrible crime."

Police said that by Monday morning, 192 people had been arrested to be charged with engaging in organised crime.