Nabila Rehman was picking okra in her family garden last year when missiles from a drone rained down from the sky, killing her grandmother and injuring her and seven other children.

The nine-year-old Pakistani girl now has a question for the US government: "What did my grandmother do wrong?"

Rehman's father has traveled with her from Pakistan's North Waziristan region to Washington, along with her 13-year-old brother, who was also wounded by shrapnel, to put a human face on America's drone campaign.

Their account was cited last week in an Amnesty International report that demanded an end to secrecy around the drone attacks and questioned US claims the missile strikes in Pakistan's tribal belt are carried out only against imminent threats with minimal civilian casualties.

Nabila's father, Rafiq Rehman, said he accepted an invitation from a documentary production company to come to the United States because "as a teacher, I wanted to educate Americans and let them know my children have been injured."

"My daughter does not have the face of a terrorist and neither did my mother. It just doesn't make sense to me, why this happened," he told AFP in an interview.

The Rehmans said they have no connection to any anti-US extremists or Al-Qaeda militants, and as they mourned their grandmother, they were confounded by inaccurate accounts of the October 2012 bombing raid.

Media reports afterward confirmed a drone strike took place, but said missiles hit a house, with one version alleging a car was struck and several militants killed.

But the Rehmans said no building or car was directly hit in the attack, and that paved roads are some distance away. They say missiles landed in the field where their grandmother was teaching Nabila how to recognize when okra are ripe enough to pick.

After a loud boom, "where my grandmother was standing, I saw these two bright lights come down and hit her," said Nabila. "And everything became dark at that point."

She noticed blood on her hand and tried to wipe it away with her shawl. "But the blood just kept coming," she said.

Shrapnel lodged in her right hand and she was treated at a local hospital. Her brother, Zubair, suffered shrapnel wounds to his left leg, which required two operations. His family had to take out a loan to pay for the surgery.

Since the attack, Zubair said he has trouble sleeping and no longer goes outside to play cricket.

"I don't feel like going outside and playing with my friends. I don't feel like going to school. It's really destroyed my life," he said.

His sister said the US government's explanation for drone strikes did not apply to her family.

"When I hear that they are going after people who have done wrong to America, then what have I done wrong to them? What did my grandmother do wrong to them?

"I didn't do anything wrong," she said.

The Rehman family's experience features in a new documentary, "Unmanned: America's Drone Wars," which takes a critical view of the air strikes.

On Tuesday, the Rehmans will appear at a press conference in Washington with a member of Congress, Alan Grayson, a Democrat from Florida.

"When it comes to national security matters like drone strikes, it's important that we hear not only from the proponents of these attacks, but also from the victims," Grayson said in a statement.

In their village in North Waziristan, there is the constant buzz of drones overhead and even small children learn to identify the sound, the father said.

Rehman said all he wanted was "peace" and to end the violence that claimed his 63-year-old mother.

"I believe there are better ways to go about it than these drones, perhaps through discussions and negotiations with whoever they are targeting."

The US government insists the drone strikes are a legal means of "self-defense" and an effective tool in the fight against Al-Qaeda, arguing other methods would put more lives at risk.

Rehman's Pakistani lawyer, Shahzad Akbar, who represents others who say they are victims of drone strikes, had planned to accompany the Rehmans but the State Department denied him a travel visa for the trip, according to Jennifer Gibson, a lawyer with Reprieve, which works with Akbar.

The Rehmans "are not asking for money. They want answers," she said.

"They hope that by coming here and saying we're the faceless people who you keep counting as numbers, somebody is going to start listening and questioning if this is really a smart policy."