"They form a roll call of heroes that would be the envy of any nation," Secretary-General Kofi Annan declared, standing beneath the very flag - now damaged - that had flown above the UN compound in Iraq on 19 August when the massive blast killed 22 people, including top envoy Sergio Vieira de Mello.

"If people need an example of our United Nations family at its best and brightest, at its most committed and most courageous, they have only to look at the men and women who perished in the Canal Hotel," he added as family members and others in the audience wiped away tears.

"When we lost them, our Organization also suffered another loss, of a different kind: a loss of innocence for the United Nations," he said after paying homage by name to each of the victims. "We, who had assumed that our mission to help others served as its own and ultimate form of protection, now find ourselves threatened and exposed. We, who have tried from the beginning to serve those targeted by violence and destruction, have become targets ourselves."

But despite the new need to balance the mission to help others with the needs of self-protection, "our commitment - our pledge in the name of 'we the peoples' - must never change," Mr. Annan concluded. "Today, let us renew that commitment in the name of our irreplaceable, inimitable, unforgettable friends. Let us work to heal these unhealable wounds, by working every day to live up to the standard they set us."

After a minute of silence and musical tribute from a cellist, members of the bereaved families in turn moved forward to light a candle in memory of each of the victims.

Poems were read in homage. Then the flag from that August afternoon was lowered by the honour guard from above the tribune - sullied, dirtied, holed, revered as a symbol of UN heroism.

Video of memorial ceremony