A United Nations investigation into targeted killings will examine drone strikes in Afghanistan, Pakistan, Yemen and Somalia, according to the British lawyer heading the inquiry.

Ben Emmerson QC, a UN special rapporteur, will reveal the full scope of his review which will include checks on military use of unmanned aerial vehicles (UAVs) in UK operations in Afghanistan, US strikes in Pakistan, as well as in the Sahel region of Africa where the conflict in Mali has erupted. It will also take evidence on Israeli drone attacks in Palestinian territories.

About 20 or 30 strikes – selected as representative of different types of attacks – will be studied to assess the extent of any civilian casualties, the identity of militants targeted and the legality of strikes in countries where the UN has not formally recognised there is a conflict.

The inquiry will report to the UN general assembly in New York this autumn. Depending on its findings, it may recommend further action. Emmerson has previously suggested some drone attacks – particularly those known as "double tap" strikes where rescuers going to the aid of a first blast have become victims of a follow-up strike – could possibly constitute a "war crime".

The inquiry will be co-ordinated through Emmerson's UN office in Geneva. Among the team of experts working with him will be the former director of public prosecutions, Lord Macdonald QC, a former prosecutor at the international criminal tribunal for the former Yugoslavia, Sir Geoffrey Nice QC, and Dr Nat Cary, one of the UK's most experienced pathologists who specialises in the interpretation of injuries caused by explosions.

The inquiry is the result of a request by several nations, including Pakistan and two permanent members of the UN security council.

Staff in Geneva have already begun to examine details of individual drone strikes. Emmerson says that, when assembled, his dossier of evidence may not lead to direct "attribution of legal liability" but will enable him to put allegations to the states responsible and obtain a response.

The Ministry of Defence, he said, had assured him of its willingness to co-operate. The influential US Council on Foreign Relations recently recommended that the US president should: "provide information to the public, Congress, and UN special rapporteurs – without disclosing classified information – on what procedures exist to prevent harm to civilians".

Despite many US officials justifying drone strikes in Yemen, Pakistan and Somalia as acceptable as part of the global war on terrorism, others in the Washington administration have more recently acknowledged a need to demonstrate legal justification for targeted killings to the international community.

Emmerson told the Guardian: "One of the fundamental questions is whether aerial targeting using drones is an appropriate method of conflict … where the individuals are embedded in a local community.

"One of the questions we will be looking at is whether, given the local demography, aerial attacks carry too high a risk of a disproportionate number of civilian casualties." "The explosion of drone technology [raises the question whether] the military dependence on UAVs carries an unacceptably high risk of civilian casualties."

Between June 2004 and September 2012, according to research by the Bureau of Investigative Journalism, drone strikes killed between 2,562 and 3,325 people in Pakistan, of whom between 474 and 881 were civilians, including 176 children.