PORTLAND, US - A gunman opened fire Tuesday in an Oregon laboratory, killing a female worker before fatally shooting himself in the third gun rampage in the United States in less than a week, police said.

Police in the Portland suburb of Tualatin confirmed to AFP that the suspected shooter was one of two fatalities in the incident, which occurred shortly before 12:00 pm local time (1900 GMT).

An unidentified woman died at the scene of the shooting at Legacy Medical Laboratories while the suspected gunman was also declared dead of a "self-inflicted gunshot wound," police spokeswoman Jessica Massey said.

The gunman had entered the facility armed with a rifle and fired "multiple shots." Two other people were wounded in the attack and were being treated at area hospitals. The extent of their injuries was not clear.

Local television networks reported eyewitnesses as seeing a woman wearing a white lab coat from the laboratory with multiple wounds to her lower leg.

The attack took place as the United States mourned a gun rampage by a US army major at Fort Hood military base in Texas last Thursday which left 13 people dead and 42 wounded.

On Friday one person was killed and five wounded after a mass shooting at an office building in Orlando, Florida blamed by police on a disgruntled ex-worker who was later arrested. --AFP