A UN expert is launching a special investigation into the drone warfare and targeted killings that the United States uses in its global war against al Qaida, Belfast Telegraph said.

The civilian killings and injuries that result from drone strikes on suspected terrorist cells will be part of the focus of the investigation by British lawyer Ben Emmerson.

He is the UN special expert on human rights and counter-terrorism, based in the Geneva office of the UN Commission on Human Rights.

Mr Emmerson's report will go to the UN General Assembly later this year.

His office says countries that use drones have "an international law obligation to establish effective independent and impartial investigations into any drone attack in which it is plausibly alleged that civilian casualties were sustained".