DNA tests have established that an Air Force airman arrested this week in a string of Colorado sexual assaults is the so-called "Center City rapist," responsible for a series of rapes and a murder in Philadelphia, authorities said Wednesday.

Philadelphia Police Commissioner Sylvester M. Johnson said the tests show a match between the genetic fingerprint of the man who raped five Philadelphia women and murdered a sixth in the late 1990s, and the Colorado suspect, Senior Airman Troy Graves.

Graves, 29, was arrested Tuesday and ordered held on $1 million bail in connection with six sexual assault cases from May to August 2001 in Fort Collins, Colo., near the Colorado State University campus.

Philadelphia District Attorney Lynne Abraham said her office on Thursday would seek a warrant against Graves. It would amend a warrant prosecutors filed in December that had charged the DNA of an unknown man with the crimes.

"I'm tremendously relieved that it appears we have the man who is responsible for the cases in Philadelphia," Abraham said.

Citing a gag order issued by a Colorado judge, Abraham and Johnson declined to release further information.

The man who came to be known as the Center City rapist attacked four Philadelphia women in the summer of 1997, then struck again on May 7, 1998, strangling 23-year-old graduate student Shannon Schieber in her apartment. A sixth victim was raped in her apartment in August 1999.

Philadelphia police had said DNA tests showed that the six attacks were committed by the same man. Not knowing the suspect's identity and concerned about the nearing five-year statute of limitations on rape under Pennsylvania law, authorities filed a warrant against the DNA of the unknown man.

In September, police announced that further DNA tests had concluded that the same person was also responsible for several unsolved attacks in Fort Collins.

In both cities, the intruder entered apartments through unlocked doors or windows in the early morning, blindfolded his victims and forced them to perform a sex act.