* U.N. chief condemns "terrible act"
* Security chief to probe breach of defenses - spokesman (Adds comments by U.N. spokesman, Nigerian ambassador)
By Patrick Worsnip
UNITED NATIONS, Aug 26 (Reuters) - U.N. Secretary-General Ban Ki-moon condemned Friday's car bomb attack on U.N. offices in Nigeria's capital, Abuja, and said the casualty toll would likely be "considerable," although he had no exact figures.
In a statement to reporters, he said he was sending his deputy, Asha-Rose Migiro, to Nigeria immediately to meet officials in Abuja. Migiro, who is Tanzanian, will be accompanied by U.N. security chief Gregory Starr.
Abuja police said at least 18 people were killed. [ID:nL5E7JQ1D2]
The U.N. Security Council opened a previously scheduled meeting on peacekeeping by standing for a minute's silence in honor of the Abuja victims.
"We do not yet have precise casualty figures but they are likely to be considerable," Ban said. "A number of people are dead; many more are wounded."
He said the bombed building housed premises for 26 U.N. humanitarian and development agencies.
"This was an assault on those who devote their lives to helping others," Ban said. "We condemn this terrible act, utterly."
U.N. spokesman Farhan Haq said the Abuja building had been well protected, but that Starr, who formerly worked for the U.S. State Department's diplomatic security unit, would "try to see what we could learn better about how our defenses were breached."
A 2007 attack on a U.N. building in Algiers, which killed at least 41 people, including 17 U.N. staff, led to the resignation of Starr's predecessor, Briton David Veness, as allegations arose the facility had been inadequately defended.
Haq said there was a series of barriers outside the Abuja building. "There was a way, it seems, in which this particular vehicle or an explosive device got through. In other words, the car got through a couple of gates that were defended by security guards," he told reporters.
"How that happened, how they got past security, we'll need to determine," he said.
Haq said the United Nations had been improving security at buildings around the world. He declined to say what the threat level had been in Abuja but said there had been no previous threat against the building.
Nigerian U.N. Ambassador Joy Ogwu described the attack as "transnational terrorism."
She told reporters: "This new threat on the institution of the United Nations should be met with a new response. I think at this time we should begin, as an institution, to step up efforts to bring to book the perpetrators of these crimes."
Ogwu did not elaborate. (Editing by Peter Cooney)
Our Standards: The Thomson Reuters Trust Principles.
