Baghdad, Iraq ? Even before the fatal bombing at the United Nations headquarters in Iraq, anxiety was growing among its staff as the summer wore on and security deteriorated, U.N. officials said.

A U.N. World Food Program had come under grenade attack July 6 in the northern city of Mosul, killing an Iraqi driver. Two weeks later, assailants attacked a Red Cross vehicle, killing an aid worker from Sri Lanka and wounding the Iraqi driver.

A security plan to fortify the world body’s operations in Iraq had been sent to the New York headquarters, where it was awaiting approval at the time of the Aug. 19 suicide truck bombing, said a senior U.N. official, who like other U.N. employees contacted by The Associated Press would speak only on condition of anonymity.

But a suicide attack of that magnitude had not been envisioned. And even if the world body had implemented the planned security measures before the bombing, the steps would not have protected the Canal Hotel from the sort of massive explosion that sheared off a side of the three-story building, killing at least 23 people and wounding more than 100, he said.

The official said events in Baghdad “were beyond what anyone expected.”

According to a U.N. official in New York, it would be reasonable that a decision on a security issue would take days or weeks. “It’s a big organization, and there are a lot of missions out there,” the official said.

After the attack, which was unprecedented in the history of the organization, the United Nations sped up planned security projects in the Iraqi capital and ordered an overall review, the senior U.N. official in Baghdad said. Barricades have been placed across streets at the headquarters and satellite offices in Baghdad to prevent open vehicle access.

On Tuesday, 5,000 U.N. employees participated in silent marches in Geneva and New York. The U.N. Staff Union said it organized them to mourn those killed and to demand “a full and independent investigation” into security at the Baghdad offices.

Before the attack, some 30 U.S. soldiers watched the outside of the U.N. compound. A high concrete wall had recently been constructed around the hotel, but because of property lines, it was — in some places — not far from the building itself.

The wall was only about 20 feet from the office of chief envoy Sergio Vieira de Mello, who died in the attack. The truck carrying the bomb was parked there.