(Recasts with remarks to staff, paragraphs 4,5,6)

By Lamine Chikhi

ALGIERS, Dec 18 (Reuters) - The United Nations will not be intimidated by the "terrifying" attack that killed 17 of its staff in Algiers, U.N. Secretary-General Ban Ki-moon said on Tuesday after visiting its ruined offices in Algeria's capital.

"I cannot tell you how shocked I was, how saddened and distressed I was by this terrible event," Ban, on a one-day visit, told U.N. staff after inspecting the devastated site of one of the Dec. 11 bombings claimed by al Qaeda.

"What I saw before me was awful, and now that I see before me the families of the victims, I have no words to say how profoundly I feel about what has happened. I see these children and I have no words to express my emotions."

"But we will not be intimidated, we will not be discouraged," he said of the attack, one of twin bombings the same day which killed at least 37 people in Algiers.

He later told reporters on his departure from Algiers for New York: "The impact of the attack was terrifying ... All the U.N. agencies will continue their work in Algiers."

The attacks were the second big bombing this year in the capital of the OPEC member country, seeking to rebuild after civil strife in the 1990s which killed up to 200,000.

Witnesses said Ban was driven in a heavily guarded convoy of vehicles to the city's Hydra district where he inspected crumpled blocks of masonry at the site of the ruined offices of the U.N.'s refugee agency and the U.N. Development Programme.

Reporters were not permitted to accompany Ban to the site.

The second suicide car bombing on Dec. 11 damaged the Constitutional Court building in Ben Aknoun district.

Al Qaeda's North African wing claimed responsibility for the suicide bombings, saying it had targeted what it called "the slaves of America and France".

Ban also met President Abdelaziz Bouteflika, saying Algeria and the world body had decided to work together closely to fight terrorism. Ban, who said the two men also discussed climate change, illegal migration and the Western Sahara question, added the U.N. expected to obtain other offices in Algiers shortly.

The United Nations has identified the dead U.N. employees as 14 Algerians and one victim each from Denmark, Senegal and the Philippines.

At Ban's meeting with staff, U.N. Development Programme (UNDP) Algeria Representative Marc de Bernis gave Ban the U.N. flag that was flying at the offices when it was struck.

UNDP Administrator Kemal Dervis said during a visit to Algiers last week that the United Nations was boosting security at its offices around the world after Tuesday's attacks, but he said this would need more funding. (Reporting Abdelaziz Boumzar and Lamine Chikhi, Writing by William Maclean; Editing by Charles Dick)

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