Drone attacks in Pakistan and Yemen against alleged terrorists have killed innocent civilians instead and have violated international laws, according to two human rights groups that released reports today.

Amnesty International said the cases it investigated may even amount to war crimes and it's calling for investigations into the attacks, along with Human Rights Watch.

Human Rights Watch issued a 97-page report Tuesday that examines six incidents, most using armed drones, from 2009 to 2013. At least 57 civilians died because of the strikes, which killed 82 people.

"Two of the six cases that we examined in my report show that the U.S. indiscriminately killed civilians. This is a clear violation of international law, even if it was not the U.S. intent. If it indiscriminately killed it should be held responsible," Letta Tayler, one of the report's authors, said at a news conference in Washington, D.C., Tuesday morning.

Human Rights Watch researchers spent six weeks in the country interviewing nearly 100 people, including witnesses and relatives, about the strikes.

"Yemenis told us that these strikes make them fear the U.S. as much as they fear Al-Qaeda in the Arabian Peninsula," Tayler said in a news release.

All six attacks either killed civilians indiscriminately, targeted illegitimate military objectives or caused disproportionate civilian deaths, according to the report.

During these operations, the U.S. government may be using "an overly elastic definition of a fighter who may be lawfully attacked during an armed conflict," the group said.

The American government and Yemeni authorities both declined to comment on the investigation.

Grandmother killed in field

Amnesty International released a separate report Tuesday on U.S. drone strikes in Pakistan that also alleges "unlawful killings" have taken place.

The group reviewed 45 known drone strikes that took place in North Waziristan in northwestern Pakistan between January 2012 and August 2013. Researchers interviewed witnesses and victims, and the report includes stories such as a grandmother who was killed while picking vegetables in a field, surrounded by her grandchildren when she died. Eighteen labourers, including a 14-year-old boy, were killed in another strike while they were sitting outside eating.

“We cannot find any justification for these killings. There are genuine threats to the USA and its allies in the region, and drone strikes may be lawful in some circumstances. But it is hard to believe that a group of labourers, or an elderly woman surrounded by her grandchildren, were endangering anyone at all, let alone posing an imminent threat to the United States,” Mustafa Qadri, one of the researchers, said in a news release.

At the joint news conference with Human Rights Watch, Qadri said the deaths "appear to be war crimes" but that there is a lot of information that is unknown and it is up to the U.S. government to provide it, he said.

"We are very concerned about these cases being war crimes," Qadri said.

Human Rights Watch did not raise the issue of possible war crimes in its report but said there are at least two cases of "clear violations of international law" and strong evidence of violations in the four other strikes it investigated.

Both organizations are calling for U.S. Congress to investigate the cases outlined in the two reports and any other potentially unlawful strikes.

"The U.S. should investigate attacks that kill civilians and hold those responsible for violations to account," Tayler said. "It’s long past time for the U.S. to assess the legality of its targeted killings, as well as the broader impact of these strikes on civilians."

The groups not only placed blame on the American government but also said the Pakistani government has failed to protect its citizens or enforce their rights — including compensation — after an attack.

U.S. 'acting like hit and run driver'

They are also pushing for more transparency from both governments and are calling for the facts and legal basis for the attacks that were carried out in Pakistan and Yemen. If anyone is found to be responsible for unlawful killings, they want them to be held accountable in a courtroom.

"It is time to end the black hole of accountability for drone strikes. The U.S. has acted like a hit and run driver, refusing to take responsibility for the killings of a 68-year-old woman and a 14-year-old boy among others," said Naureen Shah, an Amnesty International advocate who was at the news conference.

Human Rights Watch admits the applicability of international humanitarian law is sometimes unclear, adding America's battle with al-Qaeda does "not appear to meet the intensity required under the laws of war to amount to an armed conflict."

However, America should still follow international human rights law, said the organization, which only permits using deadly force "when strictly and directly necessary to save human life."

White House press secretary Jay Carney said the administration is "reviewing those reports carefully," and defended the use of drones, saying the U.S. is choosing a course of action that is least likely to result in civilians being killed.

He disputed the assertion that the U.S. has acted contrary to international law and said "extraordinary care" is taken to ensure it is followed.

"U.S. counterterrorism operations are precise, they are lawful and they’re effective," Carney told reporters.