UN rights boss asks US for facts on bin Laden killing

But Navi Pillay, U.N. High Commissioner for Human Rights, said that the al Qaeda leader, killed in a U.S. operation in Pakistan, had committed crimes against humanity as self-confessed mastermind of "the most appalling acts of terrorism", including the Sept. 11, 2001 attacks on America.

It was always clear that taking bin Laden alive was likely to be difficult, she said, noting that U.S. authorities had stated that they intended to arrest him if possible.

"This was a complex operation and it would be helpful if we knew the precise facts surrounding his killing. The United Nations has consistently emphasised that all counter-terrorism acts must respect international law," Pillay said in a statement issued in response to a Reuters request.