CIA drone attacks in Pakistan are responsible for unlawful killings, some of which could amount to war crimes, Amnesty International says.
Amnesty said it reviewed nine recent drone strikes in North Waziristan and found a number of victims were unarmed.
In a separate report looking at six US attacks in Yemen, Human Rights Watch says two of them killed civilians at random, violating international law.
Drone warfare has become common in the US pursuit of al-Qaeda and the Taliban.
Few details are known about the covert US drone operation.