SAN FRANCISCO (Reuters) - A federal appeals court on Friday ruled that Tucson shooting suspect Jared Loughner must return to a federal prison facility in Missouri for psychiatric treatment.

A three-judge panel of the U.S. Ninth Circuit Court of Appeals said Loughner's attorneys had failed to demonstrate that Loughner would suffer "irreparable harm" by being sent back to the facility in Springfield, Missouri.

"Loughner has been determined to require psychiatric treatment and will be involuntarily medicated for the immediate future whether or not he is transported to the Missouri facility," the panel said in a brief written ruling.

Loughner, 23, has pleaded not guilty to 49 criminal counts, including first degree murder, in a January 8 shooting spree outside a supermarket that killed six people and wounded 13 others, including U.S. Representative Gabrielle Giffords.

The Arizona Democrat, who was meeting with constituents outside a supermarket at the time, was shot through the head and is still recovering.

U.S. District Judge Larry Burns in May found Loughner mentally unfit to stand trial and ordered the college dropout to be treated for four months at the Missouri prison facility.

On September 28, Burns found that progress had been made toward restoring Loughner's mental competency and ordered him to remain there for four more months of treatment.

Defense attorneys sought to have that ruling overturned and have repeatedly asked the courts to halt their client's forcible medication by doctors at the Missouri facility.

The Ninth Circuit's brief ruling on Friday did not address the issue of forcing him to take medication.

(Writing and reporting by Dan Whitcomb; Editing by Greg McCune)