A gunman who killed three people in what police described as a random attack was being hunted Tuesday in the western US state of Washington.

Following two mass shootings in California that killed 18, the United States is once again grappling with the horror of escalating gun violence.

Police in the city of Yakima said, as quoted by AFP, that a man killed three people at a convenience store overnight in an apparently unprovoked attack.

"It appears to be a random situation," Yakima Police Chief Matthew Murray said.

"There was no apparent conflict between the parties. They just walked in and started shooting," Murray added.

Murray detailed that officers were examining surveillance footage from the area around the Circle K store after the attack at 3:30 am.

"The first shooting was inside the store. Then he came outside the store and shot a victim outside the store and then went across the street and apparently shot one more person," the Police Chief said as quoted by AFP.

"We have three confirmed deceased parties," he reported.

Police first assumed a fourth person was in the car but later stated that no other individuals were injured.

"This is a dangerous person and it's random so there is a danger to the community," he said.

"We don't have a motive, we don't know why. We will do everything we can to locate and apprehend that person," he added.

Yakima is a city of about 100,000 people located 100 miles (160 kilometers) southeast of Seattle.

On Monday, seven people were killed at two agricultural locations south of San Francisco.

On Saturday night, an elderly man rampaged through a dance studio in Monterey Park near Los Angeles, killing 11 people who had gathered for Lunar New Year celebrations.

Huu Can Tran committed suicide several hours later as police moved in on his van.

Recently, the United States has been rocked by a succession of high-profile mass shootings, including in schools, churches, grocery stores, and hospitals. The incidents have collectively left dozens dead.