UNHCR is still in shock over the recent brutal killing of staff member Zill-e-Usman, who was shot by unidentified gunmen in the Katcha Gari camp on the border of the Federally Administered Tribal Areas in Pakistan's North-West Frontier Province. Another staff member, Ishfaq Ahmad, was wounded in the July 16 incident. A guard working with the Commissionerate for Afghan Refugees, a government-funded agency, was also killed. Four to five gunmen reportedly opened fire on Mr. Usman as he was walking back from the camp administrative office to his car during a routine visit to the site.

Mr. Usman was the third UN refugee agency staff member to be killed in Pakistan this year. On June 9, Aleksandar Vorkapic died in the bombing of the Pearl Continental Hotel in Peshawar; on February 2, Syed Hashim, UNHCR senior driver, was killed in the kidnapping of John Solecki, head of the Quetta office, who was later released.

As I wrote to Mr. Usman's family, his murder is a cruel blow. There is no justification for attacks on humanitarian workers dedicated to the protection and care of the world's most vulnerable people. The killing of Mr. Usman was an outrage and a tragedy that affects us all.

This August 19, on the occasion of the first ever World Humanitarian Day, we will pause to remember Mr. Usman and hundreds of other UN and non-governmental organization workers who have lost their lives while carrying out their duties around the world. The date is important: it was on August 19, 2003, that a massive bomb blast in Baghdad took the lives of then UN Special Representative Sergio Vieira de Mello and 21 others.

The ongoing death toll of humanitarian workers raises fundamental questions about how we can ensure staff security in unstable environments.

Globally, it reminds us of the major dilemma facing humanitarian agencies around the world - how do we meet the life-or-death needs of the world's most vulnerable people while making sure those who provide that help are kept safe? Our ability to assist those who need it most is being severely tested by the shrinkage of the so-called 'humanitarian space' in which we must work. The nature of conflict is changing, with a multiplicity of armed groups -- some of whom view humanitarians as legitimate targets.

Another example of this is the brutal murder last month of Ms. Natalia Estemirova, a staff member of UNHCR's partner, Memorial, in the Russian Federation. Ms. Estemirova was found dead in the North Caucasus region of Ingushetia following her abduction from her home in Chechnya. Since 2000, in addition to her work as a prominent human rights investigator, Ms. Estemirova had been a social worker with Memorial and its UNHCR-funded legal and social counselling project in Grozny. She worked on issues related to internally displaced people in Chechnya and their safe return to their homes. Memorial has been an implementing partner of UNHCR in the North Caucasus since 2000 and received UNHCR's annual Nansen Refugee Award in 2004.

Humanitarian personnel work in the most dangerous places in the world and risk their own lives in the effort to help vulnerable populations to preserve theirs. Ensuring staff safety must be a top priority of every humanitarian organization and the United Nations as a whole. This is non-negotiable.

And yet, with the evolving nature of armed conflict and the changing attitudes of some belligerents, the deliberate targeting of humanitarian workers has increased, establishing a tension -- and in some situations a contradiction -- between the imperatives of staff safety and humanitarian action. UNHCR has continuously struggled to determine the 'acceptable' level of security risk to which its staff members can be exposed.

As this month's commemoration demonstrates, it is a truly terrible dilemma.

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