Three teenagers and a 20-year-old man were shot and wounded outside a Portland, Oregon, high school when a gunman thought to have gang ties opened fire following a dispute, police said.

The suspect, believed to be in his early teens or early 20s, fled the scene with two other males following the shooting on Friday less than a block from Rosemary Anderson High School and all three remained at large several hours later, said Pete Simpson of the Portland Police Bureau.

A 16-year-old girl who was struck by the gunfire shortly after noon outside the school in north Portland was rushed to a local hospital, where she was listed in critical condition, Simpson said.

A 17-year-old boy and 20-year-old man were in serious condition at the same hospital and a 19-year-old female was treated and released after being grazed in the foot by a bullet.

Simpson said all of the victims were students at the school or in related job training programmes

History of violence

Rosemary Anderson is an alternative high school for dropouts and other at-risk or homeless students.

After being placed on lockdown and searched by police, the school reopened later on Friday afternoon.

Officers with search dogs combed nearby neighbourhoods for the suspect, Simpson said, adding that the area had a history of violence but had not seen a shooting with an injury in about four years.

He said preliminary information suggested the shooter had gang ties.

Portland police have said they saw a spike in gang crime this summer and have complained they do not have adequate resources to address the problem.

Recent violence includes a man killed in a drive-by-shooting in June and another man killed in a separate shooting. A 5-year-old boy also was shot in the leg while playing at an apartment complex.

There was another school shooting in the Portland area in June, but it was not gang-related. A freshman killed another boy in a locker room and a bullet grazed a teacher before the shooter went into a bathroom and died from a self-inflicted gunshot, police said.

Source: Agencies