Crowds cheered Arizona congresswoman Gabrielle Giffords as she left a Tucson hospital where she stunned doctors with her recovery two weeks after being shot in the head in an assassination bid.

The 40-year-old Democrat was moved in an ambulance to a plane bound for Houston, Texas, for rehabilitation on Friday. A doctor with her said Giffords heard them and smiled, and tears welled up in her eyes.

Children sat on their parents' shoulders as the motorcade passed. Many waved and others carried signs wishing Giffords, known as Gabby, well.

"It was very emotional and very special," said Dr Randall Friese.

A gunman shot the congresswoman and 18 other people on 8 January as she met constituents outside a supermarket in Tucson. Six people died in the rampage, including Arizona's top judge, John Roll. The suspected gunman, Jared Loughner (22), is in federal custody. His motive is not known.

After her 930-mile trip, Giffords was in an intensive care unit at Texas Medical Centre this weekend, where a new team of doctors planned to start her therapy immediately. After several days of evaluation, she will be sent to the centre's rehabilitation hospital, TIRR Memorial Hermann.

Giffords has "great rehabilitation potential", said Dr Gerardo Francisco, chief medical officer of Memorial Hermann. "She will keep us busy, and we will keep her busy as well," he said.

The first thing is to determine the extent of her injuries and the impact on her abilities to move and communicate. She has not spoken yet and it is unknown whether she will suffer permanent damage. Since the attack Giffords has made progress nearly every day, with surgeons calling her improvement remarkable.

Because part of her skull was removed during surgery, a specially-made helmet was made to protect her brain. Friese said Giffords' husband asked them to make another one, with the Arizona flag on it.