A shooting has left "multiple victims" at an elementary school in the northwestern US state of Oregon, police said, adding that the shooter is dead.

"We don't have confirmation yet who shot the suspect. It may have been a bystander. At this time, we have multiple victims," said Sheila Miller, a spokesperson at the Bend Police Department, in a press conference on Thursday.

The Bend-La Pine School District said in a statement on social media that the Silver Rail Elementary School was under lockdown.

An updated post later said law enforcement was escorting students in buses to a separate location, where families could reunite with their children.

Miller said that officers were alerted to respond to a critical scene at 1:00 pm local time, and that police were on the scene approximately two minutes later.

"Seconds later, we received word over the radio that the suspect in this incident was down," she said.

Miller said medics had taken at least two people to a local hospital, adding that "we do not know their status."

The school is more than 160 kilometres southeast of the city Portland. It serves primary-age students in kindergarten through fifth grade.

Senator Jeff Merkley from Oregon said he and his team are "closely" monitoring the situation.

"As details continue to come out, my heart is with the Bend community and all of the students and families affected. No one should have to fear violence at school," Merkley said on US social media company X.

World's most heavily armed society

The United States, where firearms are readily available, is a frequent scene of gun violence, with thousands of people killed every year.

It has the highest rate of gun-related deaths among all developed nations.

The deadliest school shooting in US history took place at Virginia Tech on April 16, 2007, when South Korean student Seung-Hui Cho killed 32 people and wounded 17 others before taking his own life.

There have been more than 360 mass shootings in the United States so far this year, according to the Gun Violence Archive, which defines a mass shooting as four or more people shot.

Persistent mass shootings in the US have repeatedly heightened public calls for stricter federal gun control measures.

Despite repeated calls over the years, the US Congress has yet to enact such restrictions.

The United States holds the highest rate of civilian firearm ownership globally, making it the world's most heavily armed society.