A SEVEN-year-old boy has drowned after becoming trapped under a submerged tree trunk in a river near the Kalumburu.

Police say the boy was swimming with other children in the King Edward River, near the northern Kimberley community of Kalumburu, when fast-flowing waters pinned him under the tree trunk at around 1pm (WST) yesterday.

Police and volunteers freed the boy but he couldn't be revived after being underwater for about 20 minutes.