The United States has carried out "unlawful killings" in Pakistan with drone attacks and should be held to account, Amnesty International stated Tuesday.

The U.K.-based international rights group's report was released on the eve of Pakistani Prime Minister Nawaz Sharif's meeting with President Barack Obama on Wednesday, when the use of drones is expected to be high on the agenda.
The report documents killings in Pakistan's north-western tribal areas.

Some of those killings could amount to war crimes or extrajudicial executions, Amnesty International says.

People in the tribal belt live in constant terror of death from such drones, according to the report, titled "Will I be next? U.S. drone strikes in Pakistan."

The group slammed the U.S. for an "almost complete absence of transparency" on the drone programs.

"Secrecy surrounding the drones program gives the U.S. administration a license to kill beyond the reach of the courts or basic standards of international law," said Mustafa Qadri, the Pakistan researcher for Amnesty International.

It is time for the U.S. "to come clean about the drones program," he said in a statement. "What hope for redress can there be for victims of drone attacks and their families when the U.S.A. won't even acknowledge its responsibility for particular strikes?"

In the report, the group reviewed 45 known drone strikes in North Waziristan from January 2012 to August 2013. The region has seen more strikes than any other parts of Pakistan. It conducted detailed field research into nine of the 45 strikes.

A 68-year-old grandmother, Mamana Bibi, was killed in a double strike - apparently by a Hellfire missile - in October 2012 while she was picking vegetables in family fields surrounded by a handful of her grandchildren, the report read.

In July 2012, 18 laborers, including a 14-year old boy, were killed in multiple strikes on an impoverished village close to the border with Afghanistan as they were getting ready for an evening meal after work.

The report blamed such killings on "signature strikes" - attacks in which the victim's identity is unknown, but their age, gender and behavior appears suspicious. Such strikes have been on the rise during the Obama administration.

"Anyone who grows a beard and has a gun and drives a car - people think he might be a Taliban fighter," the report quotes a resident of Esso Khel, one of the most drone-affected areas in North Waziristan, as saying.

"But over here every man carries a gun, so you cannot tell who is Taliban and who is just a local in his village."

The group also documented cases of so-called "rescuer attacks," in which those who ran to the aid of a drone victims were themselves targeted in a follow-on attack.

The U.S. continues to rely on a "global war" doctrine to attempt to justify a borderless war with Al-Qaida, the Taliban and those perceived to be their allies, the report alleged.

The secrecy surrounding the drones program "has enabled the U.S. to act with impunity and block victims from receiving justice or compensation," the group said.

"As far as Amnesty International is aware, no U.S. official has ever been held to account for unlawful killings by drones in Pakistan."

"The tragedy is that drone aircraft deployed by the U.S. over Pakistan now instill the same kind of fear in the people of the tribal areas that was once associated only with Al-Qaida and the Taliban," said Qadri.

The group asked U.S. authorities to disclose facts about and the legal foundation for the drone strikes.

"The international community should oppose U.S. drone strikes and other killings that violate international law, and refrain from participating in any way in U.S. drone strikes that violate international law, including by sharing intelligence or facilities," the report stated.

In May, Obama gave the first official confirmation of the drone program, defended the policy as legal and set up new steps for transparency. But he failed to address criticism of "signature strikes" and expectations he would move the drone program from the CIA to the Pentagon.