US politician Gabrielle Giffords is to step down this week from US Congress to focus on her recovery.

Ms Giffords, a Democrat representing Arizona, was shot in the head in a shooting spree in Tucson a year ago.

Six people died and 12 others were wounded in the shooting on 8 January 2011 targeting Ms Giffords first congressional outreach meeting of the year in Tucson.

23-year-old Jared Loughner was arrested and charged with crimes, including attempting to assassinate Ms Giffords.

He pleaded not guilty, and was found unfit to stand trial.

"I have more work to do on my recovery, so to do what is best for Arizona I will step down this week," Gabrielle Giffords said in an announcement on social media such as Twitter and YouTube.

"I'm getting better. Every day my spirit is high. I will return and we will work together for Arizona and this great country. Thank you very much," she added.