A newly-announced UN inquiry into the rise of drone strikes and targeted killings around the world has drawn measured optimism and concerns from national security experts and the international human rights community.

Ben Emmerson QC, the UN special rapporteur on counter-terrorism and human rights, announced on Thursday that he will head an inquiry examining the impact of drone strikes on civilian populations in five countries: Pakistan, Afghanistan, Yemen, the Palestinian territories and Somalia.

"The aim of the inquiry is to shine the light of truth on the competing allegations that there are disproportionate civilian casualties on the one hand and that there are few or no civilian casualties on the other," Emmerson told the Guardian. "The critical lacuna in the debate that is currently taking place within the United Nations concerning the legality of drone strikes is the absence of independent, objective verification of the facts."

While 51 states possess the technology to use drones, according to Emmerson, the US is responsible for the vast majority of the world's drone strikes and the practice of targeted killing has become a central component of the Obama administration's efforts to combat al-Qaida. According to the Bureau of Investigative Journalism, CIA drone strikes in Pakistan alone have resulted in as many as 3,461 deaths, including up to 891 civilians.

Critics of the Obama administration's targeted killing program argue that it is utterly lacking in transparency and accountability. US officials have claimed the administration is in the midst of completing a targeted killing rule book and have said decisions as to who it kills are the result of a careful and deliberate process. Emerson hopes the UN inquiry will provide the Obama administration with an opportunity to make its case publicly.

"I have every reason to believe that the United States believes itself to have a case that it wishes to be made public," he said. "Members of the administration have made it clear to me that they consider that they have a case to make and I hope and expect that they will regard this engagement with the inquiry as an opportunity to do that."

Emerson acknowledges that national security concerns could limit the details the US can provide to the inquiry but believes a "very considerable amount of information" could be shared on "appropriate terms of confidentiality" provided the disclosures are "subject to assurances that nothing would be made public without an opportunity to respond."

"I would very much hope to be given the gist of the essential principles and access to the critical information concerning the available technology," Emmerson added. "There is, as I have emphasized, absolutely no agenda here other than accountability and transparency."

The Obama administration is currently the target of a lawsuit filed by the American Civil Liberties Union and the Center for Constitutional Rights over the deaths of three American citizens killed by US drones in Yemen. On Thursday the ACLU expressed hope that the inquiry would reign in the administration's targeted killing campaign.

"We welcome this investigation in the hopes that global pressure will bring the US back into line with international law requirements that strictly limit the use of lethal force," Hina Shamsi, director of the ACLU's National Security Project, said in a statement. "Virtually no other country agrees with the U.S.'s claimed authority to secretly declare people enemies of the state and kill them and civilian bystanders far from any recognized battlefield. To date, there has been an abysmal lack of transparency and no accountability for the US government's ever-expanding targeted killing program."

Joshua Foust, a fellow at the American Security Project with experience working for the US on security issues in Afghanistan and Yemen, welcomed the prospect of reliable information on targeted killings.

"I wish the UN all the luck in the world in getting anything concrete out of the US government about this," Foust told the Guardian. Noting that the inquiry focuses largely on US and Israeli conflict zones, Foust said: "Neither country has been particularly forthcoming about the kind of detail that they want to investigate. If they're able to somehow get that information, that's great, and I think the public will benefit from having that kind of information be out there."

Foust added, however, that the success of the inquiry hinges on the co-operation of the nations in question and that historically the UN has lacked the authority to compel information. "I have a feeling that what they're really going to accomplish is demonstrating how toothless the UN is at getting solid information," he said. "One of the classic problems with UN investigations is that they can't coerce countries to comply with them."

Foust noted an "equal danger" that Emmerson's inquiry could become "a vehicle whereby anti-drone activists can get a UN ruling in their favor and not necessarily an empirical or even objective rights-based view of what's really happening. That's the other side of it, but I think it entirely comes down to who he decides to partner with and ultimately who he's able to get to agree to speak with him."

Gregory Johnsen, a Princeton PhD candidate and author of the new book, The Last Refuge: Yemen, al-Qaeda and America's War in Arabia, argued the inquiry was the result of a failure on the part of US lawmakers to sufficiently challenge the Obama administration on its expansive targeted killing program. Under the administration, the US has conducted numerous air strikes in Yemen, including several in recent weeks resulting in at least 18 deaths. Two US drone strikes in 2011 resulted in the deaths of three Americans, including 16-year-old Abdulrahman al-Aulaqi.

"I think this is a case in which the US Congress has refused to challenge the Obama administration's claims that the drone strikes it carries out around the world are 'ethical and just,' and because of its refusal someone else has stepped up to challenge the administration's 'trust us' argument," Jonhsen told the Guardian.

"Yemen is a deeply divided country that is barely being held together at the moment, which will obviously present challenges for the investigators," he added. Johnsen suggested that UN investigators may find it difficult to determine the level of threat posed by individuals the US has killed in Yemen.

"In addition to women and children, I think one of the most difficult and potentially divisive issues will be: how the investigators count the male casualties of drone strikes? Are they tribesmen, members of Aqap, or both? One of the major problems is that men whom the US targets as terrorists are often defended as tribesmen."