Family and friends have gathered at the St Elizabeth Ann Seton Catholic Church for the funeral of the youngest victim of the Arizona shootings.

Nine-year-old Christina Taylor Green was killed on Saturday during a shooting spree that claimed six lives and left congresswoman Gabrielle Giffords battling for her life.

Green was born on September 11 2001, the day of suicide aircraft attacks on the US. A stars and stripes flag pulled from the rubble of the World Trade Center in the days after Christina's birth was brought in to hang between two fire truck ladders outside of the church.

Several family members' eyes filled with tears as they looked at the flag before entering the church. They then escorted the small coffin into the church in silence.

Green's funeral will be followed on Friday by that of federal judge John Roll, who was gunned down alongside her after he called in at the "Congress on the corner" event to see Giffords, who was a friend.

Police have arrested a 22-year-old college dropout, Jared Lee Loughner, for the killings.