Doctors for Rep. Gabrielle Giffords (D-Ariz.) on Thursday cited "very encouraging" signs in her recovery process, including opening her eyes and lifting her arm unexpectedly Wednesday night.

At a press conference at University Medical Center, Trauma and Critical Care Director Dr. Peter Rhee and Chief of Neurosurgery Dr. Michael Lemole said Giffords was beginning to become aware of her surroundings and was making spontaneous movements with her left arm and both legs. They said she had begun aggressive physical therapy on Thursday.

Giffords, who was severely injured Saturday in a shooting attack that killed six and wounded more than a dozen, had opened her eyes and lifted an arm Wednesday night in front of close friends and colleagues, including House Minority Leader Nancy Pelosi. Doctors called that a "major milestone."

President Obama, who also visited Giffords but was not in the room at the time, announced during his speech at a memorial service Wednesday for the shooting victims that Giffords had surprised everyone by opening her eyes for the first time. He got a rousing response.

Lemole described the scene in the hospital room.

"I was there when she was surrounded by her friends from the Congress and Senate, and I think it was a combination of the unexpected and familiar to open her eyes and look around," he said.

Lemole said it was "very, very encouraging" that Giffords was able to open her eyes and that she had enough command to move them "wherever she wants to go."

"She's starting to become aware of her surroundings," he said.

With respect to physical therapy, Rhee said Giffords is capable of sitting up and lifting her legs. Lemole stressed the importance of that kind of control. "That's huge," Lemole added.

But the doctors remain cautious despite the very promising signs, saying they would closely monitor Giffords for pneumonia and bloodclots that can be potentially very dangerous.

"Going forward we want to make sure that she doesn't backslide," Lemole said. "But I have to say this is a major leap forward, this is a major milestone for her and we hope that she crosses through many more."

Rhee said one of the next milestones will be removal of her breathing tube, though Giffords is capable of breathing on her own at this point. Doctors may do a tracheotomy in the coming days.

"She still has the tube in her throat, but even though she's still on the machine she's breathing on her own with warm humidified air," Rhee said.

"A lot of medicine is out of our control," Lemole said. "We're wise to acknowledge miracles."

Of the 20 victims of the shooting, six died and all but six have been discharged from the hospital. One — Giffords — is in critical condition, four have improved to fair condition and one is being discharged Thursday, the doctors said.

"Everybody is making fantastic forward progress," Rhee said.