Massacre children were collateral damage, says Oklahoma bomber

Mass killer Timothy McVeigh says children who died in the Oklahoma City bomb massacre were "collateral damage", according to a new book.

Details in the book mark the first time McVeigh has publicly and explicitly admitted to the crime and given his reasons for the 1995 attack which killed 168 people, 19 of them children .

The phrase "collateral damage" is how the US military refers to civilian deaths that result from strikes against the enemy. McVeigh served in the Gulf war.

"I understand what they felt in Oklahoma City. I have no sympathy for them," McVeigh told the authors of American Terrorist: Timothy McVeigh and the Oklahoma City Bombing. He had no control over the book's content.

McVeigh told Lou Michel and Dan Herbeck, reporters for The Buffalo News, he did not know there was a day care centre inside the Alfred P. Murrah Federal Building, the authors said on the American television show PrimeTime Thursday.

"I recognised beforehand that someone might be ... bringing their kid to work," McVeigh said, according to the ABC broadcast.

"However, if I had known there was an entire day care centre, it might have given me pause to switch targets. That's a large amount of collateral damage."

Michel said McVeigh's only regret was that the children's deaths proved to be a public relations nightmare.

Danny Defenbaugh, the FBI's lead investigator in the case, said he had no doubt McVeigh knew before the bombing that children would be among his victims.

McVeigh, 32, is scheduled to be executed May 16.