LOS ANGELES (AFP) - Armed police locked down an Oregon high school on Tuesday after reports that shots had been fired, TV pictures showed, although there were no immediate reports of casualties.

Some 60 law enforcement officers and 19 medical personnel descended on the Reynolds High School in the northwestern US state, according to local Koin television.

Children could be seen in live TV images filing out with their hands up, as police scrambled to deal with America's latest shooting incident at a school.

About an hour after the incident started around 8am, CNN reported that the situation was "contained" at the school, just outside Portland, Oregon.