A bomb exploded on Saturday outside a California fertility clinic, killing one person in what the FBI labeled a terror attack.

The blast tore through downtown Palm Springs, ripping a hole in the clinic and blowing out the windows and doors of nearby buildings, a journalist on the scene reported.

"Make no mistake, this is an intentional act of terrorism," Akil Davis, the head of the FBI's Los Angeles field office told reporters near the site of the fatal explosion.