The United Nations is launching an inquiry into the impact on civilians of drone strikes and other targeted killings.
UN special rapporteur Ben Emmerson, QC, who is heading the investigation, said there is a need for "accountability and reparation where things have gone badly wrong".
The British lawyer said the "exponential" rise of drone technology required a proper legal framework to be put into place.
The inquiry will study the impact of drone strikes in five places, the BBC reports. Twenty-five attacks will be examined - in Pakistan, Afghanistan, Yemen, the Palestinian territories and Somalia.
Mr Emmerson told journalists in London that the increasing use of drones "represents a real challenge to the framework of international law".
If unregulated, the use of drones would continue to grow, he said.
Ben Emmerson has previously said some kinds of drone attacks could constitute a war crime, according to the Guardian.
The inquiry will assess the extent of civilian casualties, the identity of militants targeted and the legality of strikes where there is no UN recognition of a conflict.
Defenders of drones say they minimise civilian casualties, but opponents say drone strikes can constitute extra-judicial killing and point to data suggesting hundreds of civilians have died in such strikes.