The United Nations special rapporteur on human rights and counterterrorism, Ben Emmerson, is formally launching an inquiry into the effects of drone strikes on civilians.
In a statement, the Office of the UN Commissioner for Human Rights said the investigation will focus on a "critical examination of the factual evidence concerning civilian casualties."
Emmerson will make recommendations to the UN General Assembly about "the duty of states to conduct effective independent and impartial investigations into the lawfulness and proportionality of such attacks."
Drone strikes have been controversial during the past few years.
Senior U.S. officials have declared them to be an effective weapon against terrorist leaders, but some Western activists and Pakistani and Afghan politicians blame them for killing civilians indiscriminately.