HOUSTON — A shootout among members of several rival motorcycle gangs in a busy shopping plaza in the Central Texas city of Waco on Sunday left at least nine bikers dead and 18 others injured, creating chaos in a sprawling parking lot packed with afternoon shoppers, law enforcement officials said.

The gunfire erupted about 12:15 p.m. outside a Twin Peaks Restaurant, where members of the motorcycle clubs had gathered. The fight spilled into the parking lot, initially involving just fists and feet, but escalating quickly to chains, knives, clubs and firearms. Waco police officers were already at the scene when the confrontation unfolded because they had anticipated problems as hundreds of bikers from at least five groups gathered at the shopping plaza.

“There were multiple people on the scene firing weapons at each other,” Sgt. Patrick Swanton, a Waco Police Department spokesman, said at a news conference. “They then turned on our officers. Our officers returned gunfire, wounding and possibly killing several.”

Law enforcement officials said the shootout was the worst violence in Waco since the siege on the Branch Davidian compound in 1993 that left 86 people dead. On Sunday, eight members of motorcycle clubs were killed at the scene and another died at a hospital, Sergeant Swanton said. The injured were taken to hospitals with gunshot and stab wounds.